feat: add --extra-header flag for custom gRPC headers

[sputnikraket]

Signed-off-by: Erik Hennings erik.hennings@freda.com

Description

This PR adds support for passing custom headers to gRPC requests via a new --extra-header flag.

Testing

Manual testing

References

[github-actions]

CLA Assistant Lite bot All contributors have signed the CLA ✍️ ✅

[sputnikraket]

I have read the CLA Document and I hereby sign the CLA

[tstirrat15]

I think this is fine, but what's the use case? I'm wondering if it's something that zed already supports.

[radhus]

I think this is fine, but what's the use case? I'm wondering if it's something that zed already supports.

We're running SpiceDB behind a proxy that requires authentication (GCP Cloud Run), that can be specified either through the Authorization header or another header. So we kind-of need to pass double authentication tokens 😅

This setup is perhaps not ideal, but it works.

[tstirrat15]

See question; otherwise LGTM

[tstirrat15]

Does this logic functionally merge the headers, or would this overwrite headers if some other component added new headers?

[codecov-commenter]

Codecov Report

❌ Patch coverage is 7.31707% with 38 lines in your changes missing coverage. Please review.
✅ Project coverage is 41.49%. Comparing base (56e9ecd) to head (67dafa8).

Files with missing lines	Patch %	Lines
internal/client/client.go	5.40%	34 Missing and 1 partial ⚠️
internal/testing/test_helpers.go	0.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #588      +/-   ##
==========================================
- Coverage   41.72%   41.49%   -0.23%     
==========================================
  Files          38       38              
  Lines        6131     6172      +41     
==========================================
+ Hits         2558     2561       +3     
- Misses       3317     3354      +37     
- Partials      256      257       +1     

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