Next group of API changes focused around more flexibility when interacting with httpx through generated clients. Primary motivation is to make working around some of the other limitations of generated clients easier.

Examples:

1. Ability to pass through custom headers / cookies
2. Ability to access more details from the response (e.g. status code, response headers, raw body)
3. Generate endpoints containing unsupported features? (e.g. let them pass through the pieces we didn't support and return raw response if we don't know how to parse)