[BUG] [JAVA] Using allOf to wrap a $ref as an array item generates a different object.

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

OAS spec = v3.0.3

With the version 6.0.0, when wrapping a $ref with allOf on an array item, a new model is generated. That new model is the one used as the object type for the array instead of the original being referenced by $ref.

Note: We wrapped the $ref with allOf so that we can add sibling "xml.name"

5.4.0 behavior (expected):

public class Errors   {

  @JsonProperty("errors")
  @JacksonXmlProperty(localName = "errors")
    @XmlElement(name = "error")
  @Valid
  private List<Error> errors = new ArrayList<>();

6.0.0 behavior:

public class Errors   {

  @JsonProperty("errors")
  @JacksonXmlProperty(localName = "errors")
    @XmlElement(name = "errors")
  @Valid
  private List<ErrorsErrorsInner> errors = new ArrayList<>();

openapi-generator version

6.0.0

OpenAPI declaration file content or url

schemas:
    Errors:
      description: The list of errors related to the API
      type: object
      required:
        - errors
      properties:
        errors:
          type: array
          items:
            allOf:
              - $ref: '#/components/schemas/Error'
            xml:
              name: 'error'
      xml:
        wrapped: true
        name: 'errors'
    Error:
      description: A detailed error related to the API
      type: object
      properties:
        code:
          description: The error code
          type: string
          example: '1111111'
        message:
          description: A human-readable description of the error for debugging purposes
          type: string
          example: 'The email has not been provided'
        field:
          description: The name of the field provided in the original request (if any) that the error pertains to
          type: string
          example: 'email'
      xml:
        name: 'error'

Generation Details

We are using openapi-generator-maven-plugin on a java project.
-- mvn clean install

Steps to reproduce

• Create an object and add an array as a paramter
• Reference another object as the array item and wrap it with allOf

Related issues/PRs

Suggest a fix

OAS 3.1.0 allows $ref to have sibling which eliminates the need to wrap it with allOf... but is not yet supported by openapi generator as far as I know.

Start with the provided OAS 3.0.3 schema and the openapi-generator-maven-plugin, then run the documented mvn clean install reproduction. Compare the generated Errors model with the expected Java snippet; done means the array uses Error and preserves the XML item name error rather than generating ErrorsErrorsInner with errors.