Add support for github enterprise instance (GHEC) or potentially other types of github instances

[simchri]

Hello!

thought it might be valuable to share a modification that I have been using personally now for a few days.

The issue: My company gives us access to copilot, but only through their private GitHub Enterprise (.Com) instance. I love the plugin but could only continue to use it by changing the hardcoded urls to point to our instance. However, this could also be made configurable. So proposition:

• introduce config keys for setting basically the github url
• adjust the built-in copilot provider to use configurable urls

PR : https://github.com/CopilotC-Nvim/CopilotChat.nvim/pull/1343#issue-3331918809 feedback very welcome, I am completely new to lua :)

Regards!

[wojtuss]

@deathbeam , any plans for adding this support? Thank you!

[deathbeam]

Yes its last planned thing for 5.0.0, just did not got around to adding it yet