Move metric image upload path and change type

Add spec

changelogs/unreleased/sarnold-metric-image-upload-route.yml

+---
+title: Add direct upload acceleration for metric images
+merge_request: 653
+author:
+type: added

internal/upstream/routes.go

@@ -267,6 +267,9 @@ func (u *upstream) configureRoutes() {
 		// Group Import via UI upload acceleration
 		u.route("POST", importPattern+`gitlab_group`, upload.Accelerate(api, signingProxy, preparers.uploads)),
 
+		// Metric image upload
+		u.route("POST", apiPattern+`v4/projects/[0-9]+/issues/[0-9]+/metric_images\z`, upload.Accelerate(api, signingProxy, preparers.uploads)),
+
 		// Explicitly proxy API requests
 		u.route("", apiPattern, proxy),
 		u.route("", ciAPIPattern, proxy),

upload_test.go

@@ -120,6 +120,7 @@ func TestAcceleratedUpload(t *testing.T) {
 		{"POST", `/import/gitlab_project`, true},
 		{"POST", `/import/gitlab_group`, true},
 		{"POST", `/api/v4/projects/9001/packages/pypi`, true},
+		{"POST", `/api/v4/projects/9001/issues/30/metric_images`, true},
 	}
 
 	for _, tt := range tests {