Integrate Empirical with Google Vertex AI

[archie-ai-code-explain-pr-review]

• Empirical currently supports Gemini models via Google API keys, which are accessed through Google AI Studio and Google Workspaces
• The user's company uses Vertex AI within Google Cloud, which is accessed through IAM policies/application default credentials, rather than API keys
• Integrating Vertex AI with Empirical could provide access to a wider range of models, including those from Google, Anthropic, Mistral, and others
• The user is unsure if this integration is possible, but believes it would be beneficial