[BUG][SPRING] Example string generation does not compile when using "$ref"

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

When generating "spring" code for an endpoint that returns an array and the object definition is a "$ref" and the object definition has an example, the generated code contains a string that doesn't compile. The backslashes of the example are wrongly escaped.

openapi-generator version

5.2.0

OpenAPI declaration file content or url

https://gist.github.com/benfonty/98c445d969b84896019d6c09bcb25ccd

Generation Details

openapi-generator generate -i test-api.json -g spring -o ./generated

Steps to reproduce

openapi-generator generate -i test-api.json -g spring -o ./generated

Try to build the generated code.

There is an error in ./generated/src/main/java/org/openapitools/api/TestApi.java.

String exampleString = "{ \"adminUser\" : \"{\\"userName\\":\\"admin.user@example.com\\"}\", \"id\" : \"id\" }";

Start by running the shown openapi-generator command with the linked test-api.json specification and inspect ./generated/src/main/java/org/openapitools/api/TestApi.java. Trace the Spring generator path that produces exampleString; done means the generated Java builds successfully without the escaping error and the "$ref" array case remains covered.