Cleanup request http method/code metrics

Remove 13 of the 93 request method codes from Prometheus metrics
intialization. Reduces un-used/extremely rare metrics by 14%

Filter method label by the list of valid request methods.
Signed-off-by: Ben Kochie <bjk@gitlab.com>

changelogs/unreleased/bjk-rack_metric_methods.yml

+---
+title: Cleanup request http method/code metrics
+merge_request: 42618
+author:
+type: performance

lib/gitlab/metrics/requests_rack_middleware.rb

@@ -4,15 +4,13 @@ module Gitlab
   module Metrics
     class RequestsRackMiddleware
       HTTP_METHODS = {
-        "delete" => %w(200 202 204 303 400 401 403 404 410 422 500 503),
-        "get" => %w(200 204 301 302 303 304 307 400 401 403 404 410 412 422 429 500 503),
-        "head" => %w(200 204 301 302 303 304 400 401 403 404 410 429 500 503),
+        "delete" => %w(200 202 204 303 400 401 403 404 500 503),
+        "get" => %w(200 204 301 302 303 304 307 400 401 403 404 410 422 429 500 503),
+        "head" => %w(200 204 301 302 303 401 403 404 410 500),
         "options" => %w(200 404),
-        "patch" => %w(200 202 204 400 403 404 409 416 422 500),
-        "post" => %w(200 201 202 204 301 302 303 304 400 401 403 404 406 409 410 412 413 415 422 429 500 503),
-        "propfind" => %w(404),
-        "put" => %w(200 202 204 400 401 403 404 405 406 409 410 415 422 500),
-        "report" =>  %w(404)
+        "patch" => %w(200 202 204 400 403 404 409 416 500),
+        "post" => %w(200 201 202 204 301 302 303 304 400 401 403 404 406 409 410 412 422 429 500 503),
+        "put" => %w(200 202 204 400 401 403 404 405 406 409 410 422 500)
       }.freeze
 
       HEALTH_ENDPOINT = /^\/-\/(liveness|readiness|health|metrics)\/?$/.freeze
@@ -48,6 +46,7 @@ module Gitlab
 
       def call(env)
         method = env['REQUEST_METHOD'].downcase
+        method = 'INVALID' unless HTTP_METHODS.key?(method)
         started = Time.now.to_f
 
         begin