[BUG] [Spring] [Java] additionalModelTypeAnnotations not applied to enums

Created by: ondrakucera

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• What's the version of OpenAPI Generator used?
• Have you search for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Bounty to sponsor the fix (example)

Description

Option additionalModelTypeAnnotations isn't applied to enums.

openapi-generator version

4.3.0

OpenAPI declaration file content or url

swagger: "2.0"
info:
    title: Book
    version: 1.0.0
paths:
    /books:
        get:
            summary: Get books
            responses:
                200:
                    description: Successful response
                    schema:
                        type: array
                        items:
                            $ref: '#/definitions/Book'
definitions:
    Book:
        description: Book
        type: object
        properties:
            type:
                $ref: '#/definitions/BookType'
    BookType:
        description: Book type
        type: string
        enum:
            - HARDCOVER
            - PAPERBACK
            - ELECTRONIC

Command line used for generation

generate -g spring -p additionalModelTypeAnnotations=@Foo,hideGenerationTimestamp=true
generate -g java -p additionalModelTypeAnnotations=@Foo,hideGenerationTimestamp=true

Steps to reproduce

Generate the code and see the following:

Book.java:

...
/**
 * Book
 */
@ApiModel(description = "Book")
@Foo

public class Book   {
  ...
}

BookType.java

/**
 * Book type
 */
public enum BookType {
  ...
}

Related issues/PRs

Suggest a fix