Generating doc for entities with map attribute does not work

[tonithomsson]

Generating doc for entities with map attribute does not work

1. Create a SpringBoot project with jdk17 at
   https://start.spring.io/#!type=gradle-project&language=java&platformVersion=2.6.7&packaging=jar&jvmVersion=17&groupId=com.example&artifactId=demo&name=demo&description=Demo%20project%20for%20Spring%20Boot&packageName=com.example.demo&dependencies=data-rest,data-mongodb,web

2. Add dependencies:
   implementation 'org.springdoc:springdoc-openapi-ui:1.6.8'
   implementation 'org.springdoc:springdoc-openapi-data-rest:1.6.8'

3. Create a interface and model:
   @RepositoryRestResource
   public interface PersonRepository extends MongoRepository<Person, String> {
   }

public class Person {
@id
public String id;
public String name;

@DocumentReference
public Map<String, Person> friends = new HashMap<>();

}

4. Start app and open http://localhost:8080/swagger-ui/index.html
   causes the following error:
   2022-04-26 22:31:23.236 ERROR 93367 --- [nio-8080-exec-6] o.a.c.c.C.[.[.[/].[dispatcherServlet] : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is java.lang.IllegalArgumentException: Mismatched number of generics specified for private static class org.springdoc.data.rest.core.DataRestResponseService$MapModel] with root cause

java.lang.IllegalArgumentException: Mismatched number of generics specified for private static class org.springdoc.data.rest.core.DataRestResponseService$MapModel
at org.springframework.util.Assert.isTrue(Assert.java:139) ~[spring-core-5.3.19.jar:5.3.19]
at org.springframework.core.ResolvableType.forClassWithGenerics(ResolvableType.java:1088) ~[spring-core-5.3.19.jar:5.3.19]
at org.springframework.core.ResolvableType.forClassWithGenerics(ResolvableType.java:1074) ~[spring-core-5.3.19.jar:5.3.19]
at org.springdoc.data.rest.core.DataRestResponseService.resolveGenericType(DataRestResponseService.java:361) ~[springdoc-openapi-data-rest-1.6.8.jar:1.6.8]