PMM-10461 No absolute Nginx redirects

[ademidoff]

PMM-10461

Link to the Feature Build: SUBMODULES-4055

This pull request updates the Nginx configuration in pmm.conf to improve URL rewriting logic and enhance server behavior. The main focus is on simplifying rewrite rules for Grafana and Swagger UI, and disabling absolute redirects for better control over request handling.

Nginx configuration changes:

• Disabled absolute_redirect to prevent Nginx from rewriting redirects to absolute URLs, which can help with proxy setups and custom domain handling.

Rewrite rule improvements:

• Simplified the Grafana root URL rewrite to use a permanent local redirect (rewrite ^/$ /graph/ permanent;), instead of constructing a redirect with scheme and host.
• Changed Swagger UI rewrite rules to use local permanent redirects, removing the use of $scheme and $http_host for cleaner and more predictable URL handling.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 44.51%. Comparing base (fa6ecd0) to head (68f2cb0).
⚠️ Report is 4 commits behind head on v3.

Additional details and impacted files

@@            Coverage Diff             @@
##               v3    #4576      +/-   ##
==========================================
- Coverage   44.54%   44.51%   -0.04%     
==========================================
  Files         363      363              
  Lines       45715    45715              
==========================================
- Hits        20365    20351      -14     
- Misses      23692    23706      +14     
  Partials     1658     1658              

Flag	Coverage Δ
admin	17.33% <ø> (ø)
agent	53.23% <ø> (-0.13%)	⬇️
managed	44.48% <ø> (ø)
vmproxy	74.13% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.