[BUG][CPP-UE4] Missing support for arrays with unique items

Created by: madrazzl3

Description

At the moment UE4-CPP generator creates invalid output for arrays with unique items (i.e. 'sets'). Instead of making them TSet (or TArray), it generates type 'Set' with #include "Set.h" (this code does not compile).

openapi-generator version

master / 6.0.1

OpenAPI declaration file content

type: array
items:
  type: integer
uniqueItems: true

Command line used for generation

openapi-generator generate -i openapi.yml -g cpp-ue4 -o result

Steps to reproduce

Run generation for UE4 with OpenAPI specification containing array with unique items (see schema and command line above).

Related issues/PRs

There are some of similar issues for other languages/generators, but it not so helpful.

Suggest a fix/enhancement

We need to add TSet type mapping for 'set' value type. https://github.com/OpenAPITools/openapi-generator/blob/4d947a1c4579a73c7350ea55153d33ef76ba5d89/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CppUE4ClientCodegen.java#L182