- new TInterfaceFactory.CreateFakeInstance() method for easy mocking of
      any interface, via some event callbacks
    - added TServiceMethod.DefaultResult property, to be used for stubs/mocks
    - TServiceFactory.Create() and its children will now always have an optional
      aContractExpected parameter (for consistency with TServiceFactoryClient)
    - introduce smvVariant kind of parameter for interface-based services
    - safer TInterfacedObjectFake.FakeCall() stack use


    - huge code refactoring of the ORM model implementation: a new dedicated
      TSQLModelRecordProperties will contain per-TSQLModel parameters, whereas
      shared information retrieved by RTTI remain in TSQLRecordProperties - this
      will allow use of the same TSQLRecord in several TSQLModel at once, with
      dedicated SQL auto-generation and external DB settings
    - added aExternalTableName/Database optional parameters to method
      TSQLModel.VirtualTableRegister()
................................................................................
  public
    /// the internal Instance ID, as remotely sent in "id":1
    // - is set to 0 when an entry in the array is free
    InstanceID: Cardinal;
    /// last time stamp access of this instance
    LastAccess: Cardinal;
    /// the implementation instance itself
    Instance: TObject;
    /// used to catch and ignore any exception in Instance.Free


    procedure SafeFreeInstance;
  end;

  /// server-side service provider uses this to store its internal instances
  // - used by TServiceFactoryServer in sicClientDriven, sicPerSession,
  // sicPerUser or sicPerGroup mode
  TServiceFactoryServerInstanceDynArray = array of TServiceFactoryServerInstance;
................................................................................
    // for instance, ExecuteMethod(..,'[1,2]') over ICalculator.Add will return:
    // $ {"result":[3],"id":0}
    // the returned "id" number is the Instance identifier to be used for any later
    // sicClientDriven remote call - or just 0 in case of sicSingle or sicShared
    procedure ExecuteMethod(var Ctxt: TSQLRestServerCallBackParams;
      aMethodIndex, aInstanceID: cardinal; aParamsJSONArray: PUTF8Char);
    /// this method will create an implementation instance


    function CreateInstance: TInterfacedObject;
  public
    /// initialize the service provider on the server side
    // - expect an direct server-side implementation class (inheriting from
    // TInterfacedClass or from TInterfacedObjectWithCustomCreate if you need
    // an overriden constructor)
    // - for sicClientDriven, sicPerSession, sicPerUser or sicPerGroup modes,
    // a time out (in seconds) can be defined - if the time out is 0, interface
................................................................................
      [InterfaceURI,fRest.ClassName]) else
  fImplementationClass := aImplementationClass;
  if fImplementationClass.InheritsFrom(TInterfacedObjectWithCustomCreate) then
    fImplementationClassWithCustomCreate := true;
  // initialize the shared instance or client driven parameters
  case InstanceCreation of
  sicShared: begin
    fSharedInstance := CreateInstance;
    if (fSharedInstance=nil) or
       not fSharedInstance.GetInterface(fInterface.fInterfaceIID,fSharedInterface) then
      raise EServiceException.CreateFmt('No implementation available for "%s" interface',
        [fInterfaceURI]);
  end;
  sicClientDriven, sicPerSession, sicPerUser, sicPerGroup:
    if aTimeOutSec=0 then
................................................................................

destructor TServiceFactoryServer.Destroy;
var i: integer;
begin
  try // release any internal instance (should have been done by client)
    for i := 0 to fInstancesCount-1 do
      if fInstances[i].Instance<>nil then
        fInstances[i].Instance.Free;
  except
    ; // better ignore any error in business logic code
  end;
  DeleteCriticalSection(fInstanceLock);
  inherited;
end;

................................................................................
    case fInstanceCreation of
    sicShared:
    if fSharedInterface<>nil then begin
      IInterface(Obj) := fSharedInterface; // copy implementation interface
      result := true;
    end;
    else begin
      O := CreateInstance;
      if O<>nil then
        result := O.GetInterface(fInterface.fInterfaceIID,Obj);
    end;
    end;
end;

function TServiceFactoryServer.RetrieveSignature: RawUTF8;
................................................................................
begin
  if self=nil then
    result := '' else
    result := Contract; // just return the current value
end;

procedure TServiceFactoryServerInstance.SafeFreeInstance;

begin
  try
    InstanceID := 0;
    FreeAndNil(Instance);
  except
    ; // just ignore any error in customer code
  end;
end;

function TServiceFactoryServer.InternalInstanceRetrieve(
  var Inst: TServiceFactoryServerInstance; aMethodIndex: integer): boolean;
procedure AddNew;
var i: integer;
    P: ^TServiceFactoryServerInstance;
begin
  Inst.Instance := CreateInstance;
  if Inst.Instance=nil then
    exit;
  P := pointer(fInstances);
  for i := 1 to fInstancesCount do
    if P^.InstanceID=0 then begin
      P^ := Inst; // found an empty entry -> use it
      exit;
................................................................................
end;

function TServiceFactoryServer.RestServer: TSQLRestServer;
begin
  result := TSQLRestServer(Rest);
end;

function TServiceFactoryServer.CreateInstance: TInterfacedObject;
begin
  if fImplementationClassWithCustomCreate then
    result := TInterfacedObjectWithCustomCreateClass(fImplementationClass).Create else
    result := fImplementationClass.Create;


end;

procedure TServiceFactoryServer.ExecuteMethod(
  var Ctxt: TSQLRestServerCallBackParams;
  aMethodIndex, aInstanceID: cardinal; aParamsJSONArray: PUTF8Char);
procedure Error(Msg: PUTF8Char);
begin
................................................................................
  // 1. initialize Inst.Instance and Inst.InstanceID
  Inst.InstanceID := 0;
  Inst.Instance := nil;
  case InstanceCreation of
    sicSingle:
      if aMethodIndex>=fInterface.fMethodsCount then
        exit else
        Inst.Instance := CreateInstance;
    sicShared:
      if aMethodIndex>=fInterface.fMethodsCount then
        exit else
        Inst.Instance := fSharedInstance;
    sicClientDriven, sicPerSession, sicPerUser, sicPerGroup: begin
      if InstanceCreation=sicClientDriven then
        Inst.InstanceID := aInstanceID else
................................................................................
        Factory := nil;
        Session := nil;
      end;
      WR.Free;
    end;
  finally
    if InstanceCreation=sicSingle then
      Inst.Instance.Free; // always release single shot instance
  end;
end;

function TServiceFactoryServer.AllowAll: TServiceFactoryServer;
var m: integer;
begin
  if self<>nil then

    - new TInterfaceFactory.CreateFakeInstance() method for easy mocking of
      any interface, via some event callbacks
    - added TServiceMethod.DefaultResult property, to be used for stubs/mocks
    - TServiceFactory.Create() and its children will now always have an optional
      aContractExpected parameter (for consistency with TServiceFactoryClient)
    - introduce smvVariant kind of parameter for interface-based services
    - safer TInterfacedObjectFake.FakeCall() stack use
    - TServiceFactoryServerInstance will now create instances server-side
      with a RefCount=1, to allow passing self as an interface in sub-methods
    - huge code refactoring of the ORM model implementation: a new dedicated
      TSQLModelRecordProperties will contain per-TSQLModel parameters, whereas
      shared information retrieved by RTTI remain in TSQLRecordProperties - this
      will allow use of the same TSQLRecord in several TSQLModel at once, with
      dedicated SQL auto-generation and external DB settings
    - added aExternalTableName/Database optional parameters to method
      TSQLModel.VirtualTableRegister()
................................................................................
  public
    /// the internal Instance ID, as remotely sent in "id":1
    // - is set to 0 when an entry in the array is free
    InstanceID: Cardinal;
    /// last time stamp access of this instance
    LastAccess: Cardinal;
    /// the implementation instance itself
    Instance: TInterfacedObject;
    /// used to release the implementation instance
    // - direct FreeAndNil(Instance) may lead to A/V if self has been assigned
    // to an interface to any sub-method on the server side -> dec(RefCount)
    procedure SafeFreeInstance;
  end;

  /// server-side service provider uses this to store its internal instances
  // - used by TServiceFactoryServer in sicClientDriven, sicPerSession,
  // sicPerUser or sicPerGroup mode
  TServiceFactoryServerInstanceDynArray = array of TServiceFactoryServerInstance;
................................................................................
    // for instance, ExecuteMethod(..,'[1,2]') over ICalculator.Add will return:
    // $ {"result":[3],"id":0}
    // the returned "id" number is the Instance identifier to be used for any later
    // sicClientDriven remote call - or just 0 in case of sicSingle or sicShared
    procedure ExecuteMethod(var Ctxt: TSQLRestServerCallBackParams;
      aMethodIndex, aInstanceID: cardinal; aParamsJSONArray: PUTF8Char);
    /// this method will create an implementation instance
    // - reference count will be set to one, in order to allow safe passing
    // of the instance into an interface, if AndIncreaseRefCount is TRUE
    function CreateInstance(AndIncreaseRefCount: boolean): TInterfacedObject;
  public
    /// initialize the service provider on the server side
    // - expect an direct server-side implementation class (inheriting from
    // TInterfacedClass or from TInterfacedObjectWithCustomCreate if you need
    // an overriden constructor)
    // - for sicClientDriven, sicPerSession, sicPerUser or sicPerGroup modes,
    // a time out (in seconds) can be defined - if the time out is 0, interface
................................................................................
      [InterfaceURI,fRest.ClassName]) else
  fImplementationClass := aImplementationClass;
  if fImplementationClass.InheritsFrom(TInterfacedObjectWithCustomCreate) then
    fImplementationClassWithCustomCreate := true;
  // initialize the shared instance or client driven parameters
  case InstanceCreation of
  sicShared: begin
    fSharedInstance := CreateInstance(false);
    if (fSharedInstance=nil) or
       not fSharedInstance.GetInterface(fInterface.fInterfaceIID,fSharedInterface) then
      raise EServiceException.CreateFmt('No implementation available for "%s" interface',
        [fInterfaceURI]);
  end;
  sicClientDriven, sicPerSession, sicPerUser, sicPerGroup:
    if aTimeOutSec=0 then
................................................................................

destructor TServiceFactoryServer.Destroy;
var i: integer;
begin
  try // release any internal instance (should have been done by client)
    for i := 0 to fInstancesCount-1 do
      if fInstances[i].Instance<>nil then
        fInstances[i].SafeFreeInstance; 
  except
    ; // better ignore any error in business logic code
  end;
  DeleteCriticalSection(fInstanceLock);
  inherited;
end;

................................................................................
    case fInstanceCreation of
    sicShared:
    if fSharedInterface<>nil then begin
      IInterface(Obj) := fSharedInterface; // copy implementation interface
      result := true;
    end;
    else begin
      O := CreateInstance(false);
      if O<>nil then
        result := O.GetInterface(fInterface.fInterfaceIID,Obj);
    end;
    end;
end;

function TServiceFactoryServer.RetrieveSignature: RawUTF8;
................................................................................
begin
  if self=nil then
    result := '' else
    result := Contract; // just return the current value
end;

procedure TServiceFactoryServerInstance.SafeFreeInstance;
var Obj: TInterfacedObject;
begin

  InstanceID := 0;
  Obj := Instance;
  Instance := nil;
  IInterface(Obj)._Release;

end;

function TServiceFactoryServer.InternalInstanceRetrieve(
  var Inst: TServiceFactoryServerInstance; aMethodIndex: integer): boolean;
procedure AddNew;
var i: integer;
    P: ^TServiceFactoryServerInstance;
begin
  Inst.Instance := CreateInstance(true);
  if Inst.Instance=nil then
    exit;
  P := pointer(fInstances);
  for i := 1 to fInstancesCount do
    if P^.InstanceID=0 then begin
      P^ := Inst; // found an empty entry -> use it
      exit;
................................................................................
end;

function TServiceFactoryServer.RestServer: TSQLRestServer;
begin
  result := TSQLRestServer(Rest);
end;

function TServiceFactoryServer.CreateInstance(AndIncreaseRefCount: boolean): TInterfacedObject;
begin
  if fImplementationClassWithCustomCreate then
    result := TInterfacedObjectWithCustomCreateClass(fImplementationClass).Create else
    result := fImplementationClass.Create;
  if AndIncreaseRefCount then
    IInterface(result)._AddRef; // allow passing self to sub-methods
end;

procedure TServiceFactoryServer.ExecuteMethod(
  var Ctxt: TSQLRestServerCallBackParams;
  aMethodIndex, aInstanceID: cardinal; aParamsJSONArray: PUTF8Char);
procedure Error(Msg: PUTF8Char);
begin
................................................................................
  // 1. initialize Inst.Instance and Inst.InstanceID
  Inst.InstanceID := 0;
  Inst.Instance := nil;
  case InstanceCreation of
    sicSingle:
      if aMethodIndex>=fInterface.fMethodsCount then
        exit else
        Inst.Instance := CreateInstance(true);
    sicShared:
      if aMethodIndex>=fInterface.fMethodsCount then
        exit else
        Inst.Instance := fSharedInstance;
    sicClientDriven, sicPerSession, sicPerUser, sicPerGroup: begin
      if InstanceCreation=sicClientDriven then
        Inst.InstanceID := aInstanceID else
................................................................................
        Factory := nil;
        Session := nil;
      end;
      WR.Free;
    end;
  finally
    if InstanceCreation=sicSingle then
      Inst.SafeFreeInstance; // always release single shot instance
  end;
end;

function TServiceFactoryServer.AllowAll: TServiceFactoryServer;
var m: integer;
begin
  if self<>nil then