[SPRING] Fields starting with _ are generated as duplicates

Description

When generating spring code using swagger-codegen-cli, fields starting with an _ appear in the generated response twice.

Swagger-codegen version

swagger-codegen-cli v3.0.18

Swagger declaration file content or url

defaultmodel:
    description: Default response for the api
    properties:
      api_name:
        type: string
        example: "My Wonderful API"
      api_version:
        type: string
        example: v1.0
      api_released:
        type: string
        example: "2020-02-03"
      api_status:
        type: string
        example: "active"
      _links:
        type: array
        items:
          properties:
            rel:
              type: string
              example: organisation-units
            href:
              type: string
              example: /v1.0/organisation-units
            method:
              type: string
              example: GET

Command line used for generation

java -jar swagger-codegen-cli.jar generate -i ..\api.yaml -l spring -o ..\mock

Steps to reproduce

• Generate the spring code off the api definition
• cd into the mock directory
• run mvn clean install
• run the generated jar file java -jar target\my-jar-file.jar
• Browse to localhost:8080
• Note that the _links will be present, but also another variable will be present in the response called links.

e.g.

{
  "_links": [
    {}
  ],
  "api_name": "My Wonderful API",
  "api_released": "2020-02-03",
  "api_status": "active",
  "api_version": "v1.0",
  "links": [
    {}
  ]
}

Related issues/PRs

Can't find any.

Suggest a fix/enhancement

I've reviewed the generated code and can't see this extra parameter in any of the models. It seems to be within the core swagger codegen project.

Start by running the documented swagger-codegen-cli generate command with the supplied YAML and the spring generator, then inspect the generated model and response from the jar. Trace how the _links property becomes both _links and links. Done means the generated response contains the declared _links field only, with no duplicate links field.