✨ Allow to use BYO API Keys

[roma-glushko]

This feature is frequently required in user-facing services that allows users to specify their own keys to get a cheaper pricing.
Users may bring their own keys and there needs to be a way to pass them and get in use on the Glide's end.

Use Cases

• imagine you have two price plans: service keys (more expensive) and bring your own keys (user expenses + fee on top)
  you don't want users to provide invalid keys and then allow them to use service keys if they are on BYO keys plan
• code assistance applications where users can pass their own LLM API keys