[BUG] [cpp-ue4] Missing WriteJsonValue and TryGetJsonValue for arbitrary-typed variables

Created by: madrazzl3

Bug Report Checklist

Have you provided a full/minimal spec to reproduce the issue?
Have you validated the input using an OpenAPI validator (example)?
Have you tested with the latest master to confirm the issue still exists?
Have you searched for related issues/PRs?
What's the actual output vs expected output?
[Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

This bug was brought in PR #10267, where type TSharedPtr<FJsonValue> was introduced to hold arbitrary-typed variables. However, this solution was not complete because it's missing overloads of WriteJsonValue and TryGetJsonValue functions for TSharedPtr<FJsonValue> type, that leads to compile-time errors.

openapi-generator version

master - 5.3.0

OpenAPI declaration file content or url

Full scheme

arrayOfSomething:
          type: array
          items: {}
          nullable: true

Generation Details

openapi-generator  generate -i https://gist.githubusercontent.com/madrazzl3/da2502b6816aaa98713cba75e595f373/raw/d53da8c6098167768c3e5b1ad1381467397d6a51/example-scheme.yaml -g cpp-ue4 -o generated-client/ --additional-properties=cppNamespace='api',unrealModuleName='MyAPI',modelNamePrefix=''

Steps to reproduce

Generate UE4 client with any of available tools
Try to build generated module

Related issues/PRs

Issue #10266 (closed)

Suggest a fix

We need to define proper implementations of WriteJsonValue and TryGetJsonValue for TSharedPtr<FJsonValue> type used for arbitrary-typed variables.

inline void WriteJsonValue(JsonWriter& Writer, const TSharedPtr<FJsonValue>& Value)
{
	if (Value.IsValid())
	{
		FJsonSerializer::Serialize(Value.ToSharedRef(), "", Writer, false);
	}
	else
	{
		Writer->WriteObjectStart();
		Writer->WriteObjectEnd();
	}
}

inline bool TryGetJsonValue(const TSharedPtr<FJsonValue>& JsonValue, TSharedPtr<FJsonValue>& JsonObjectValue)
{
	JsonObjectValue = JsonValue;
	return true;
}