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

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

Start with the Spring and Java generator entry points using the supplied OpenAPI definition and the additionalModelTypeAnnotations option. Compare generated Book.java with BookType.java and verify that the enum receives the configured annotation while preserving the existing model behavior.