Some fixes for older Delphi and UTF-8 Body encoding

[Dzyszla]

In Delphi 10 (or all version, where use Indy and WebBroker still base on AnsiString) the UTF8 body encoding is incorrect.

I suggest to add decoder for request with declared utf-8 or without any:

Index: Horse.Request.pas
===================================================================
@@ -268,6 +268,29 @@
   that need the raw bytes should use Body<TStream>.
   =========================================================================== }
 function THorseRequest.Body: string;
+{$IF NOT DEFINED(FPC)}
+  {$IF CompilerVersion < 36}
+	function IsUTF8OrUnspecifiedCharset(const AContentType: string): Boolean; inline;
+	var
+		LParameter: string;
+		LCharset: string;
+		LSeparator: Integer;
+	begin
+		Result := True;
+		for LParameter in AContentType.Split([';']) do
+		begin
+			LSeparator := Pos('=', LParameter);
+			if (LSeparator > 0) and SameText(Trim(Copy(LParameter, 1, LSeparator - 1)), 'charset') then
+			begin
+				LCharset := Trim(Copy(LParameter, LSeparator + 1, MaxInt));
+				if (Length(LCharset) >= 2) and (LCharset[1] = '"') and (LCharset[Length(LCharset)] = '"') then
+					LCharset := Copy(LCharset, 2, Length(LCharset) - 2);
+				Exit(SameText(LCharset, 'utf-8'));
+			end;
+		end;
+	end;
+  {$IFEND}
+{$ENDIF}
 begin
   if not Assigned(FWebRequest) then
   begin
@@ -274,6 +297,13 @@
     Result := FBodyString;
     Exit;
   end;
+  {$IF NOT DEFINED(FPC)}
+	{$IF CompilerVersion < 36}
+	// Indy JSON bytes are decoded here without linking Indy into providers that do not use it.
+	  if FWebRequest.ClassNameIs('TIdHTTPAppRequest') and (Pos('application/json', LowerCase(FWebRequest.ContentType)) > 0) and IsUTF8OrUnspecifiedCharset(string(FWebRequest.GetFieldByName('Content-Type'))) then
+		Exit(UTF8ToString(RawByteString(FWebRequest.RawContent)));
+	{$IFEND}
+  {$ENDIF}
   Result := FWebRequest.Content;
 end;