[BUG][Rust client] Generated API documentation contains obvious errors

Created by: bcourtine

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• What's the version of OpenAPI Generator used?
• Have you search for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Bounty to sponsor the fix (example)

Description

Rust client API documentation does not match generated code:

• documentation refers to a "ctx" param for auth that is never generated (auth is managed using the configuration object.
• documentation mentions that optional parameters are passed using a map object, which is false. Required and optional parameters are passed via named parameters without distinction.

openapi-generator version

master branch.

OpenAPI declaration file content or url

Not relevant.

Command line used for generation

./bin/rust-petstore.sh

Steps to reproduce

Generate Petstore example.

Suggest a fix

PR in preparation...