core/validatorapi: fix SSE proxying

[KaloyanTanev]

VC was receiving 502s on SSE

category: bug
ticket: none

[Copilot]

Pull request overview

Fixes SSE reverse-proxying in core/validatorapi that was causing validator clients to receive 502s by correcting httputil.ReverseProxy configuration for streaming requests.

Changes:

• Clear ReverseProxy.Director before setting ReverseProxy.Rewrite to avoid ServeHTTP rejecting the proxy configuration.
• Use ProxyRequest.SetURL(targetURL) in the rewrite function to correctly apply the upstream target URL for SSE requests.
• Add an internal test that spins up an upstream SSE server and verifies the /eth/v1/events stream is proxied end-to-end.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
core/validatorapi/router.go	Fixes SSE reverse proxy setup by switching cleanly to Rewrite mode and applying SetURL for correct upstream targeting.
core/validatorapi/router_internal_test.go	Adds an end-to-end SSE proxy test to ensure streaming responses work and don’t regress.

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated no new comments.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 57.09%. Comparing base (97959c4) to head (954219b).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4495      +/-   ##
==========================================
+ Coverage   56.56%   57.09%   +0.52%     
==========================================
  Files         245      245              
  Lines       32817    32826       +9     
==========================================
+ Hits        18564    18741     +177     
+ Misses      11895    11721     -174     
- Partials     2358     2364       +6     

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