Fix/key authentication

[nihiragarwal24]

Description

Added a check to verify llm api keys

Solution and Design

Whenever a user comes to the app and saves their api keys, we will once verify their api keys by calling list_models api. If it doesn't work, it surely means its a bad key

Test Plan

Tried it with bogus and verified keys. It worked perfectly.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Docs update

Checklist

• My pull request is atomic and focuses on a single change.
• I have read the contributing guide and my code conforms to the guidelines.
• I have documented my changes clearly and comprehensively.
• I have added the required tests.