protobuf 4.21 support

[gitpushdashf]

Currently, we are locked into 3.x with ~=3.13.

If I forcibly install 4.21, I get this:

E   TypeError: Descriptors cannot not be created directly.
E   If this call came from a _pb2.py file, your generated code is out of date and must b
e regenerated with protoc >= 3.19.0.
E   If you cannot immediately regenerate your protos, some other possible workarounds ar
e:
E    1. Downgrade the protobuf package to 3.20.x or lower.
E    2. Set PROTOCOL_BUFFERS_PYTHON_IMPLEMENTATION=python (but this will use pure-Python
 parsing and will be much slower).
E
E   More information: https://developers.google.com/protocol-buffers/docs/news/2022-05-0
6#python-updates

Would it be possible to regenerate with a newer protoc and allow for protobuf v4 to be used?

Thank you!

[nickgeorge]

Working on this. Turns out to be a bit annoying because there's a conflict with a json name on a Reference field... but should be able to get a solution out in a week or two.