[cpp-ue4] bug-fix issue 10205: response json parsing logging a error …

…to unreal console when there is no actual parsing problem (#10221)

* [cpp-ue4] Fixed a bug where respose json parsing was not taking 'writeOnly' or 'required' into account and was logging a error to the console when there was no actual problem.

* [cpp-ue4] Moved comments to tail of line in response to improve code appearance.  Added baseName to comments for clarity of reading.

* [cpp-ue4] removed comments from template from previous commits.

* [cpp-ue4] added back ParseSuccess flag flip for TOptional, as the templated version of TryGetJsonValue does actually handle the absense of the field correctly for TOptional.

* [cpp-ue4] reworked looping in model source template's FromJson to better mirror the loop in WriteJson

* [cpp-ue4] more concise version of writeOnly change to FromJson

modules/openapi-generator/src/main/resources/cpp-ue4/model-source.mustache

@@ -175,9 +175,14 @@ bool {{classname}}::FromJson(const TSharedPtr<FJsonValue>& JsonValue)
 
 	bool ParseSuccess = true;
 
-    {{#vars}}
+	{{#vars}}
+	{{#required}}
+	{{^isWriteOnly}}ParseSuccess &= {{/isWriteOnly}}TryGetJsonValue(*Object, TEXT("{{baseName}}"), {{name}});
+	{{/required}}
+	{{^required}}
 	ParseSuccess &= TryGetJsonValue(*Object, TEXT("{{baseName}}"), {{name}});
-    {{/vars}}
+	{{/required}}
+	{{/vars}}
 
 	return ParseSuccess;
 	{{/isString}}