Add option for Custom AI functionality using URL of OpenAI compatible API

[cmgriffing]

I would like to be able to set a custom URL for an OpenAI compatible API. This would be useful for fine tuned custom LLMs for specific projects. It would also be really useful in an Enterprise environment that wants to prevent exfiltrating data outside of their network.

It seems to me that the custom URL setting for OpenAI could be repurposed for this use case. However, a setting for a custom model name might be necessary.

[cmgriffing-at-gitkraken]

@SpaceMerlin33 Could you take a look at this Issue?