feat: forward the Argo CD logged in user to the proxy extension

[leoluz]

Will forward an additional header (Argocd-Username) to the proxy extension with the username authenticated in Argo CD.

Checklist:

• Either (a) I've created an enhancement proposal and discussed it with the community, (b) this is a bug fix, or (c) this does not need to be in the release notes.
• The title of the PR states what changed and the related issues number (used for the release note).
• The title of the PR conforms to the Toolchain Guide
• I've included "Closes [ISSUE #]" or "Fixes [ISSUE #]" in the description to automatically close the associated issue.
• I've updated both the CLI and UI to expose my feature, or I plan to submit a second PR with them.
• Does this PR require documentation updates?
• I've updated documentation as required by this PR.
• I have signed off all my commits as required by DCO
• I have written unit and/or e2e tests for my change. PRs without these are unlikely to be merged.
• My build is green (troubleshooting builds).
• My new feature complies with the feature status guidelines.
• I have added a brief description of why this PR is necessary and/or what this PR solves.
• Optional. My organization is added to USERS.md.
• Optional. For bug fixes, I've indicated what older releases this fix should be cherry-picked into (this may or may not happen depending on risk/complexity).

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 50.67%. Comparing base (e7760b5) to head (ea874aa).
Report is 6 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #19075      +/-   ##
==========================================
+ Coverage   50.64%   50.67%   +0.02%     
==========================================
  Files         315      315              
  Lines       43332    43347      +15     
==========================================
+ Hits        21947    21965      +18     
+ Misses      18879    18877       -2     
+ Partials     2506     2505       -1     

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