feat: add MiniMax as LLM provider

[octo-patch]

Summary

Add MiniMax as a first-class LLM provider to the Portkey AI Gateway, enabling seamless routing to MiniMax's advanced language models via their OpenAI-compatible API.

What's included

• Provider implementation: api.ts, chatComplete.ts, index.ts following the established provider pattern with streaming support and response transforms
• Models: MiniMax-M2.7 and MiniMax-M2.7-highspeed (204K context window, up to 192K output)
• Registration: Added to globals, provider registry, providers.json, and models.json
• Tests: 22 unit tests + 3 integration tests covering config, response transforms, streaming, and real API validation

Implementation details

• Uses open-ai-base helper for OpenAI-compatible chat completion params
• Base URL: https://api.minimax.io/v1 with Bearer auth
• Temperature default: 1.0
• Excludes unsupported params: logit_bias, logprobs, top_logprobs
• Full streaming SSE support with proper chunk transforms

Provider info

• MiniMax API Docs
• API Key env var: MINIMAX_API_KEY

Test plan

• 22 unit tests pass (provider config, API config, response transforms, stream chunk transforms)
• 3 integration tests pass (non-streaming completion, streaming completion, error handling)
• TypeScript compilation clean (no new errors)
• Prettier formatting check passes
• Build succeeds (rollup -c)

[narengogi]

@octo-patch please sign your commits

[octo-patch]

Hi @narengogi, thanks for the note! I'll rebase and sign the commits. Will push an update shortly.

[kapelame]

Just a friendly bump — this PR is already approved by @narengogi and would unblock a lot of users. MiniMax M2.7 is consistently in OpenRouter's top-10 most-used models on the monthly leaderboard, and right now Portkey users have to use the Custom OpenAI workaround to reach it.

@octo-patch are you still planning to rebase + sign? Happy to take it over (rebase your branch, sign the commits, force-push to a new branch and reopen the PR with you as co-author) if that helps move it forward.

Also happy to provide a Token Plan API key for additional verification if useful.

[kapelame]

Reopened as #1650 with the rebase + DCO sign-off applied. Same code, original author preserved via Co-authored-by:. @narengogi please review/merge there.