chore: Replace http.Method* constants with string literals

[jferrl]

Updated all usages of http.Method* constants to use string literals for HTTP methods (e.g., "GET", "POST", etc.) throughout the codebase. Added forbidigo linter to enforce this rule and updated .golangci.yml accordingly. This change aligns with new linting requirements and ensures consistency in HTTP method usage.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.12%. Comparing base (ffc5df8) to head (661a4ea).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@ Coverage Diff @@## master #3696 +/- ##
=======================================
Coverage 91.12% 91.12% =======================================
Files 187 187 Lines 16640 16640 =======================================
Hits 15164 15164 Misses 1291 1291 Partials 185 185 

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[gmlewis]

Thank you, @jferrl and @alexandear!
Merging.

[gmlewis]

@jferrl - I apologize - I spoke too soon. I forgot that another PR added forbidigo. Could you please modify this PR by consolidating the two forbidden patterns together into the same rule before I merge to make the linter happy?
Thank you!

[jferrl]

@jferrl - I apologize - I spoke too soon. I forgot that another PR added forbidigo. Could you please modify this PR by consolidating the two forbidden patterns together into the same rule before I merge to make the linter happy? Thank you!

@gmlewis fixed!

[gmlewis]

Fixes: #3695.