Add support for Grok using their Responses API compatibility #2091
Description
Description
Grok recently sent an email mentioning they are deprecating their v1/messages Anthropic compatible endpoint. They mention to use their gRPC or Responses API. They seem to have v1/chat/completions (although who knows for how long).
Seems like the best way to add support for Grok with our current system would be to add support using our existing :completions and :responses OpenAI support but pointed at Grok. This would make it easier to add support than their full gRPC client, although we have a PR that adds support (it just doesn't work as well with VCR because it's gRPC and requires custom stuff).
gRPC is likely the better longer term bet (cause it's their core SDK), but adding support sooner sounds pretty good. Nothing stopping us from doing Completions + Responses first as an easy win and tackling gRPC down the line. Worth considering how we implement things though to ensure we keep the door open for the gRPC implementation.