[Kotlin] Invalid enum var names

Created by: Zomzog

Description

When enums name start with a number, the generated code won't compile

openapi-generator version

3.0.0-SNAPSHOT

OpenAPI declaration file content or url

"enum":[
    "1name"
]

Command line used for generation

java -jar openapi-generator-cli.jar generate -i swagger.json -c config.json -l kotlin -o tmp

Steps to reproduce

Add an enum parameter to swagger file; generate and compile.

Related issues/PRs

Suggest a fix/enhancement

The enumeration name can be prefixed by an underscore, it's done like this for the model name.

Another solution is to surround illegals names with backticks, but enum may be tricky to use (Status.1available). And what I understand of kotlin coding convention is backticks are acceptable only for names in tests.