feat (provider/google-vertex): add support for maas models

[shaper]

Background

Google Vertex AI offers Model as a Service (MaaS) capabilities that allow access to partner and open models through an OpenAI-compatible API. This integration enables AI SDK users to leverage these models in their applications.

Summary

Added support for Google Vertex AI MaaS (Model as a Service) models in the AI SDK. This implementation:

• Created a new @ai-sdk/google-vertex/maas package that provides access to partner models like DeepSeek, Qwen, and Kimi
• Implemented both Node.js and Edge runtime support
• Added automatic Google Cloud authentication handling
• Integrated with the OpenAI-compatible API interface
• Added example files demonstrating text generation and streaming with various MaaS models
• Included support for tool calling functionality

Manual Verification

Tested the implementation with various MaaS models including DeepSeek, Qwen, and Kimi. Verified both text generation and streaming functionality work correctly. Also confirmed tool calling works with compatible models.

Checklist

• Tests have been added / updated (for bug fixes / features)
• Documentation has been added / updated (for bug fixes / features)
• A patch changeset for relevant packages has been added (for bug fixes / features - run pnpm changeset in the project root)
• I have reviewed this pull request (self-review)

[shaper]

• feat (provider/google-vertex): add support for maas models #11880 👈 (View in Graphite)
• main

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[chiefGui]

I know this is linked in the PR's relationships, but: in case anyone needs an interim solution: #7006 (comment)