Generate API client from Bitly OptenAPI specification

[matyama]

Bitly has an OpenAPI specification for its API - it'd probably be better (easier, more maintainable) to automatically generate the API client via a generator.

Some generators (in Rust) that come to mind:

• https://crates.io/crates/paperclip
• https://crates.io/crates/progenitor

One drawback is that the generated modes will (probably) all be fully heap allocated (or at least the generic openapi-generator does so). Although at least for the shorten command this is not strictly necessary, it probably won't be a big deal as the app is mostly I/O bound anyways.

[matyama]

After few brief experiments:

• It seems that paperclip does not have full OpenAPI v3 support yet
• On the other hand, progenitor does not support multiple response types in the spec

So this works is currently postponed (integrating the generic openapi-generator does not seem as the best choice), till required features land.