OpenAI compatible servers for suggestions

[sanderland]

Is your feature request related to a problem? Please describe.

Many platforms support an OpenAI compatible API (e.g. vllm, cohere). It would be nice to be able to use these.

Describe the solution you'd like

Add:

• An optional field for overriding the URL for openai
• An optional field for free choice of model name
• Send requests (validate key, prompt) with these parameters.

Additional context

• I've tried to make this work, but despite rebuilding with webpack, it doesn't seem to update.

[emeryberger]

Please open a PR with your changes - we will see about integrating them - thanks!

[sanderland]

Thanks! Please see #919