v2 endpoint

[ScotterC]

Here's the changelog on Cohere's side:

model is a required field for Embed, Rerank, Classify, and Chat.
embedding_types is a required field for Embed.

For Chat there are a bunch of changes in message/response structure

[andreibondarev]

@ScotterC I didn't realize there's a v2 endpoint! Why'd you close it?

[ScotterC]

@andreibondarev ha, cause I only looked into rerank endpoint and I had no idea how it might impact others. this PR was meant for my own fork to just test. Good news is the swap works just fine for rerank

[ScotterC]

Re opening since I'm moving forward with using this branch of mine and tests pass locally. Will add to it if other aspects come up. I have not directly tried endpoints other than rerank though

[andreibondarev]

@ScotterC I have a branch that I'm working on locally. I assume it makes sense to keep both the v1 and v2 endpoints side by side, what do you think?

[ScotterC]

Sounds good to me. A major version bump works as well. Thanks for all the updates!