📘 docs: Portkey AI custom endpoint in `librechat.example.yaml`

[siddharthsambharia-portkey]

Summary

Portkey AI Custom Endpoint Integration

Added configuration for the Portkey AI custom endpoint in librechat.example.yaml. This enables LibreChat users to connect directly to the Portkey API and utilize its specialized models with settings for headers, model display, and title conversations.

Key additions:

• Endpoint configuration for Portkey API
• Headers for authentication with Portkey API
• Model list and label customizations

Change Type

• [x] New feature (non-breaking change which adds functionality)

Testing

Tested the Portkey endpoint configuration by setting up the API connection with provided keys and verifying model fetching, header configurations, and response outputs. Validated model retrieval and display settings align with expected Portkey model responses.

Test Configuration:

1. Set PORTKEY_API_KEY and PORTKEY_OPENAI_VIRTUAL_KEY in environment variables.
2. Enabled caching and verified the model display label.
3. Tested response latency and accuracy for models specified in the configuration.

Checklist

• [x] My code adheres to this project's style guidelines
• [x] I have performed a self-review of my own code
• [x] I have commented in any complex areas of my code
• [x] I have made pertinent documentation changes
• [x] My changes do not introduce new warnings
• [x] I have written tests demonstrating that my changes are effective
• [x] Local unit tests pass with my changes

[siddharthsambharia-portkey]

Hey @danny-avila can you take a look at this? Thanks!