[Java] Generation of Feign Client leads to incorrect Parameter Mapping when using snake_case parameters

Description

with a snake_case Parameter, it seems that the generated Api files contains wrong Annotations to map the parameter.

  @RequestLine("GET /api/subscriptions/{subscription_id}")
  @Headers({
    "Content-Type: application/json",
    "Accept: application/json",
  })
  SubscriptionDetails getSubscription(@Param("subscriptionId") String subscriptionId);

as you can see, the @Param also contains the camelized version of the parameter, which leads to a wrong mapping (it seems that at runtime the parameter is seen as a form parameter, instead of a path parameter, as it doesnt fit the request line declaration).

is there some way to workaround this? I have read about a parameter to fix the namingProperty, but in general it would be okay for us, to have the parameters in the Java POJOS in correct camelCase, but the serialized/deserialized parameters should match the originally specified name. And I havent found it to work in our version, but maybe I configured it incorrectly.

Swagger-codegen version

2.2.2 We tried updating to a later version, but unfortunately they seemed to have incompatibilities in other features, which breaks our Unit-Tests.

Swagger declaration file content or url

 /api/subscriptions/{subscription_id}:
    get:
      operationId: getSubscription
      produces:
        - application/json
      parameters:
        - name: subscription_id
          in: path
          required: true
          type: string

Command line used for generation

<configuration>
              <language>java</language>
              <output>.</output>
              <configHelp>false</configHelp>
              <configOptions>
                <library>feign</library>
                <dateLibrary>joda</dateLibrary>
                <hideGenerationTimestamp>true</hideGenerationTimestamp>
                <interfaceOnly>true</interfaceOnly>
                <modelPropertyNaming>snake_case</modelPropertyNaming> <!-- seems to have no effect -->
                <keepUnderscores>true</keepUnderscores><!-- seems to have no effect -->
              </configOptions>
            </configuration>

Suggest a fix/enhancement

the point where the content of the @Param Annotation is set, should not contain the camlizedName, but the baseName of the Parameter, at least this is what I think is causing the problem.

Start by reproducing generation with the provided Swagger path, snake_case parameter, Feign library, and configuration options. Inspect the generated API interface containing @RequestLine and @Param, then verify that the generated parameter mapping preserves the declared path name while the Java method remains usable with camelCase naming.