feat: allow setting OPENAI_API_BASE

[Manouchehri]

What does this PR do?

Adds an optional OPENAI_API_BASE environmental. Useful if you want to use Cloudflare AI Gateway or LiteLLM;

Type of change

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

Mandatory Tasks

• Make sure you have self-reviewed the code. A decent size PR without self-review might be rejected.

Checklist

• I haven't read the contributing guide
• My code doesn't follow the style guidelines of this project (npm run prettier)
• I haven't commented my code, particularly in hard-to-understand areas
• I haven't checked if my PR needs changes to the documentation
• I haven't checked if my changes generate no new warnings (npm run lint)
• I haven't added tests that prove my fix is effective or that my feature works
• I haven't checked if new and existing unit tests pass locally with my changes

[vercel]

@Manouchehri is attempting to deploy a commit to the langfuse Team on Vercel.

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[CLAassistant]

All committers have signed the CLA.

[Manouchehri]

This would require changing some of the database stuff. Leaving it commented out for now so you can decide. =)

[Manouchehri]

I can confirm this working perfectly with LiteLLM on my end!