How do I implement "Authorization: Bearer <Token>" in a Delphi REST Server?

I have a working REST server (Sydney) that uses a custom header (AuthToken: 'Token') to authorize users.

When I try to use "Authorization: Bearer 'Token'" as a header in a POST request, I get an exception in my rest server as below.

It looks like I have to assign a procedure to a TIdHTTPParseAuthenticationEvent, but I cannot find out where to do that.

When you create a Datasnap REST server project, it creates a default TIdHTTPWebBrokerBridge object for you, which is a TIdCustomHTTPServer descendant. You can assign a handler to its OnParseAuthentication event in code (since it is not a visual component on the Form), eg:

procedure TForm1.FormCreate(Sender: TObject);
begin
  FServer := TIdHTTPWebBrokerBridge.Create(Self);
  FServer.OnParseAuthentication := ParseAuthentication; // <-- here
end;

procedure TForm1.ParseAuthentication(AContext: TIdContext;
  const AAuthType, AAuthData: String;
  var VUsername, VPassword: String;
  var VHandled: Boolean);
begin
  if TextIsSame(AAuthType, 'Bearer') then begin
    // process AAuthData and assign VUsername and VPassword as needed...
    VHandled := True;
  end;
end;

UPDATE: starting in Indy v10.6.3.3, the TIdCustomHTTPServer.DoParseAuthentication() method is now virtual, so you can alternatively derive a new class from TIdHTTPWebBrokerBridge and override it, eg:

type
  TMyHTTPWebBrokerBridge = class(TIdHTTPWebBrokerBridge)
  protected
    function DoParseAuthentication(ASender: TIdContext;
      const AAuthType, AAuthData: String;
      var VUsername, VPassword: String): Boolean; override;
  end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  //FServer := TIdHTTPWebBrokerBridge.Create(Self);
  FServer := TMyHTTPWebBrokerBridge.Create(Self);
end;

function TMyHTTPWebBrokerBridge.DoParseAuthentication(ASender: TIdContext;
  const AAuthType, AAuthData: String;
  var VUsername, VPassword: String): Boolean;
begin
  if TextIsSame(AAuthType, 'Bearer') then begin
    // process AAuthData and assign VUsername and VPassword as needed...
    Result := True;
  end else
    Result := inherited DoParseAuthentication(ASender, AAuthType, AAuthData, VUsername, VPassword);
end;