[BUG] Java client generator does not support allOf with simple types

Versions

openapi version 3.0.2
enerator version 4.0.0

Description

The java generator generates code that does not compile despite the openapi definition being valid and correctly interpreted by the swagger eidtor.

openapi: 3.0.2
info:
  title: Test API
  description: test
  version: 1.0.0
paths: {}
components:
  schemas:
    AlphaType:
      type: string
    Alpha_2:
      allOf:
        - $ref: '#/components/schemas/AlphaType'
        - minLength: 2
          maxLength: 2
          pattern: '[a-zA-Z]{2}'
    MyObject:
      type: object
      properties:
        blabla:
          $ref: '#/components/schemas/Alpha_2'

Steps to reproduce

Use swagger editor online and generate java client

Suggest a fix

The Alpha_2 should be transformed to the String class and the necessary jsr303 annotations should be added on the field.

Use the supplied OpenAPI 3.0.2 YAML with generator 4.0.0 to reproduce the Java client, then inspect the generated Alpha_2 and MyObject code. Done means the generated client compiles, Alpha_2 is represented as String, and the minLength, maxLength, and pattern constraints produce the needed JSR-303 annotations.