feat(ui-server): add forward of static headers from env

[wensiet]

Description & motivation 💭

This PR introduces static headers forwarding to gRPC temporal frontend.

Our scenario is:

• custom authorizer & claim-mapper plugin for temporal server
• TLS is provided by the infrastructure and cannot be configured
• to authenticate request, we need custom header, like x-service-auth=some-token-here
• it works with temporal-cli or SDK's, with grpc-meta, but UI only has forwarding headers, which is not suitable

To solve this issue, we introduce new env var: TEMPORAL_SERVER_STATIC_HEADERS. It is later converted to config field staticHeaders.

Format is: TEMPORAL_SERVER_STATIC_HEADERS="some-header=someval,another-header=someval"

Screenshots (if applicable) 📸

No ui components changed.

Design Considerations 🎨

No ui components changed.

Testing 🧪

Manually tested with temporal-frontend. Added unit tests to ensure logic is correct.

How was this tested 👻

• Manual testing
• E2E tests added
• Unit tests added

Steps for others to test: 🚶🏽‍♂️🚶🏽‍♀️

Add staticHeaders to configs, example:

staticHeaders:
  authorization: some-tkn

Or use ENV var TEMPORAL_SERVER_STATIC_HEADERS="authorization=some-tkn"

Checklists

Draft Checklist

Merge Checklist

Issue(s) closed

Docs

Any docs updates needed?

Yes, UI startup docs.

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