[JAVA] swagger-codgen generates code with syntax error in Enum when defined in separate definition file

Description

Swagger-codegen version

3.0.30

Swagger declaration file content or url

All source files

Command line used for generation

swagger-codegen generate -i ./api.yml -l java -o ./generated-code

Steps to reproduce

1. Keep the files api.yml, base-definitions.json and consumer.json in some directory
2. swagger-codegen generate -i ./api.yml -l java -o ./generated-code
3. cd generated code
4. mvn clean install

Related issues/PRs

Suggest a fix/enhancement

The category definitions in base-definitions.json file produces errors in read method generated in Cateogory.java

    @Override
    public Category read(final JsonReader jsonReader) throws IOException {
      Object value = jsonReader.nextString();
      return Category.fromValue(()(value));
    }

This seems to be a bug in codegen. The fix would be just to typecast the object to string i.e. generate the code as follows -
return Category.fromValue((String)(value));

Note: If we directly inline the enum inside some property instead of referring to external file definition, the issue doesn't happen and the inner class enum compiles successfully.

Start with api.yml, base-definitions.json, and consumer.json, then run the documented swagger-codegen command and inspect the generated Category.java. Build the generated project with mvn clean install and compare the external-definition enum's read method with the working inline-enum case; done means the generated Java compiles without the reported syntax error.