Support custom authorization header for access token extraction

[fsul7o]

Description

Support custom authorization header for access token extraction

Type of change

• Bug fix
• New feature
• Refactoring (no functional changes, no api changes)
• Non-code changes (update documentation, pipeline, etc.)

Flags

• Breaks backward compatibility
• Requires a documentation update
• Has untestable code

Related issue/PR

Delete this section if there are no issues or pull requests that relate to this pull request.

• Fixes #issue
• Closes #PR

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Checklist

• Followed the guidelines in the CONTRIBUTING document
• Added prefix [skip ci]/[ci skip]/[no ci]/[skip actions]/[actions skip] in the PR title if necessary
• Tested and linted the code
• Commented the code
• Made corresponding changes to the documentation
• Passed all pipeline checking

Checklist for maintainer

• Use Squash and merge
• Double-confirm the merge message has prefix [skip ci]/[ci skip]/[no ci]/[skip actions]/[actions skip]
• Delete the branch after merge

[Copilot]

Pull request overview

This PR adds support for custom authorization headers for access token extraction. Previously, the system used a hardcoded header name, but now allows configuration of which HTTP header contains the access token.

Key changes:

• Added AccessTokenAuthHeader configuration field with a default value of "Authorization"
• Updated the authorization daemon initialization to pass the custom header name to the access token parameter
• Added test coverage for both custom header and default header scenarios

Reviewed changes

Copilot reviewed 6 out of 7 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
config/config.go	Updated comment to reflect that AccessTokenAuthHeader is now supported for both gRPC and HTTP
config/config_test.go	Added expected test value for the new AccessTokenAuthHeader field
test/data/example_config.yaml	Added example configuration showing the new accessTokenAuthHeader field
usecase/authz_proxyd.go	Implemented default value logic and passed AccessTokenAuthHeader to authorization daemon initialization
usecase/authz_proxyd_test.go	Added test cases for custom header and empty header (default) scenarios
go.mod	Updated athenz-authorizer dependency and removed indirect dependencies

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