11012.Breaking

Refactored ClientRequest class. This simplifies a lot of code and improves our type checking accuracy. It also better aligns public/private attributes with what we expect developers to access safely from a client middleware.

If code subclasses ClientRequest, it is likely that the subclass will need tweaking to be compatible with the new version. Similarly, subclasses of ClientResponse may need to adjust __init__ parameters.

-- by :user:Dreamsorcerer.