Incorporate Gemini & Gemini Vision support

[supmo668]

Provide Chat Model support for Gemini

With the recent advances with Gemini and long context window features, I would like to add Gemini as a chat model available for administrator to include that as a choice of chat model.

Potentially I would like this to be assigned to me since I'd like to use it also.

[sabaimran]

Hey @supermomo668 ! First of all, agreed with your feature request, I want that too haha. Implementation-wise, we've been thinking that the best approach for adding support for additional models will be through setting up instructions for using a proxy server like LiteLLM and allowing you to set a custom openai base URL in the chat configuration.

If we do take that up as recommendation, we should certainly improve our documentation as well.

[sabaimran]

Halfway there! Gemini chat is now supported with #902 . I'll look into the vision integration in a week or two.