[ELIXIR] Inconsistency between code docs and generated code

Description

The optional params are underscored in the code documentation. But the opts keyword list requires them to be in the form given by the baseName, which is coming directly (unprocessed) from the Swagger definition.

# NOTE: This class is auto generated by the swagger code generator program.
# https://github.com/swagger-api/swagger-codegen.git
# Do not edit the class manually.

defmodule Sample.Api.Default do
  @moduledoc """
  API calls for all endpoints tagged `Default`.
  """

  alias Sample.Connection
  import Sample.RequestBuilder


  @doc """
  Add sample
  

  ## Parameters

  - connection (Sample.Connection): Connection to server
  - opts (KeywordList): [optional] Optional parameters
    - :sample_name (Somestring): Sample Name

  ## Returns

  {:ok, %{}} on success
  {:error, info} on failure
  """
  @spec add_sample(Tesla.Env.client, keyword()) :: {:ok, nil} | {:error, Tesla.Env.t}
  def add_sample(connection, opts \\ []) do
    optional_params = %{
      :"SampleName" => :body
    }
    %{}
    |> method(:post)
    |> url("/sample")
    |> add_optional_params(optional_params, opts)
    |> Enum.into([])
    |> (&Connection.request(connection, &1)).()
    |> decode(false)
  end
end

Swagger-codegen version

2.4.0-Snapshot

Swagger declaration file content or url

swagger: "2.0"
info:
  description: "Sample"
  version: "1.0.0"
  title: "Sample"
basePath: "/"

schemes:
- "http"
paths:
  /sample:
    post:
      summary: "Add sample"
      description: ""
      operationId: "addSample"
      parameters:
      - in: "body"
        name: "SampleName"
        description: "Sample Name"
        schema:
          $ref: "#/somestring"
      responses:
        405:
          description: "Invalid input"

Command line used for generation

/run-in-docker.sh generate -i sample-swagger.yaml -l elixir -o /gen/sample

Steps to reproduce

Run the command above with the provided input.

Related issues/PRs

Suggest a fix/enhancement

In the following mustache template
https://github.com/swagger-api/swagger-codegen/blob/4b9ee1f1940dba349d49dfb499b813f4cbb5858c/modules/swagger-codegen/src/main/resources/elixir/api.mustache#L37
the parameter isn't properly underscored. 'underscoring' them like in the documentation would fix it. However this introduces backward incompatibilities and I am not sure what's the policiy wrt. to such changes. Otherwise I could contribute a fix.

Start with modules/swagger-codegen/src/main/resources/elixir/api.mustache at the referenced line, then generate the sample from the provided Swagger declaration using /run-in-docker.sh. Compare the parameter spelling in the generated documentation with the opts keyword list. Done means the generated Elixir API presents and accepts consistent parameter names, with compatibility implications understood.