[Announcement][Kotlin][Retrofit][Coroutines] New generator: kotlin-retrofit

Created by: kroegerama

👋 Hello OpenAPI-Team!

I created a new generator called "kotlin-retrofit". Are you guys interested in integrating it into your repository and helping me complete/improve it?

Generator branch: kroegerama/kotlin-retrofit

Example project: Generated petstore

The main features are:

• generates a ready to use module for Android Studio
• only model classes, api classes and two helper classes are generated
• supports per-route authentication (for now: ApiKey, Basic, Bearer)
• uses kotlin data classes
• uses moshi-codegen to parse/serialize json
• uses retrofit 2.6 with support for suspend functions

The petstore.yaml works just fine right now. Also a few other apis that I tested.

Todos: _{^{(also see README.mustache)}}

• done (allOf) add better support for json schema inheritance (allOf, anyOf, etc.)
• support for collectionFormat (e.g. csv)
• add OAuth functionality
• update proguard/p8 rules for okhttp/moshi
• option to switch coroutine generation off
• add documentation
• add tests

@jimschubert @wing328 @karismann @Zomzog