idea: Add TogetherAI as a model provider

[sxflynn]

Problem Statement

As a TogetherAI user, I'd like to be able to make calls to TogetherAI and the models they offer.

Feature Idea

TogetherAI provides an OpenAI API compatible chat completion endpoint with a pay per token system and has a bunch of open models like Llama etc, not to dissimilar from the likes of Anyscale.

[imtuyethan]

• Closed in favor of roadmap: Jan has revamped Remote Engines (e.g. OpenAI, Anthropic etc) #3786
• After 0.5.14 release (10 Feb 2025), users will be able to add custom remote provider: https://jan.ai/docs/install-engines