Version 0.23.1

[tomchristie]

I think we should probably roll a 0.23.1 (or a 0.24.0) release here.

We've got a fairly substantial list of work since the latest release.

There are a couple of minor removals included here, but they're only for old undocumented aspects, so I think we're probably okay including them in a minor, but I'm happy to go with the group consensus here.

Closes #2443

0.23.1

Added

• Support for Python 3.11. (Run tests against Python 3.11 stable #2420)
• Allow setting an explicit multipart boundary in Content-Type header. (allow setting an explicit multipart boundary via headers #2278)
• Allow tuple or list for multipart values, not just list. (Allow tuple or list for multipart values #2355)
• Allow str content for multipart upload files. (Allow str content for multipart upload files #2400)
• Support connection upgrades. See https://www.encode.io/httpcore/extensions/#upgrade-requests

Fixed

• Don't drop empty query parameters. (Fix empty query params #2354)

Removed

• Drop .read/.aread from SyncByteStream/AsyncByteStream (Drop .read/.aread from SyncByteStream/AsyncByteStream #2407)
• Drop RawURL. (Drop RawURL #2241)