swagger-annotations: Add annotations to support x-enum-descriptions and x-enum-varnames

Add annotations to support x-enum-descriptions and x-enum-varnames.

More information here: https://openapi-generator.tech/docs/templating/#enum

Example
This java code:

public enum SignType {
        SIGNTYPE_PADES("PAdES"),
        SIGNTYPE_XADES("XAdES"),
        SIGNTYPE_CADES("CAdES");
        
        public final String value;
        
        SignType(String value){
            this.value = value;
        }
        
        @Override
        public String toString() {
          return String.valueOf(value);
         }
    }

Generates an openapi.json like this:

"schema" : {
                  "type" : "string",
                  "enum" : [ "PAdES", "XAdES", "CAdES" ]
                }

And Client generation produces:

public enum SignType {
        PAD_ES("PAdES"),
        XAD_ES("XAdES"),
        CAD_ES("CAdES");

}

But I needs anything like this:

public enum SignType {
        /**  Signtype PAdES */
        SIGNTYPE_PADES("PAdES"),
        /**  Signtype XAdES */
        SIGNTYPE_XADES("XAdES"),
        /**  Signtype CAdES */
        SIGNTYPE_CADES("CAdES");
...
}

I need annotations to generate x-enum-descriptions and x-enum-varnames in openapi.json file

Start by locating the swagger-annotations enum annotation handling and review the linked OpenAPI Generator enum templating documentation. Define how annotations should represent x-enum-descriptions and x-enum-varnames, then verify the shown SignType example produces the requested OpenAPI metadata and generated enum comments.