Fix GPM content types for Doorkeeper

Certain controllers (e.g. Doorkeeper::TokensController) don't expose the
method "request_format". This commit changes
Gitlab::Metrics::WebTransaction so we don't rely on this method, instead
using the underlying code this method uses.

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/46412

lib/gitlab/metrics/web_transaction.rb

@@ -28,7 +28,11 @@ module Gitlab
         controller = @env[CONTROLLER_KEY]
 
         action = "#{controller.action_name}"
-        suffix = controller.request_format
+
+        # Devise exposes a method called "request_format" that does the below.
+        # However, this method is not available to all controllers (e.g. certain
+        # Doorkeeper controllers). As such we use the underlying code directly.
+        suffix = controller.request.format.try(:ref)
 
         if suffix && suffix != :html
           action += ".#{suffix}"

spec/lib/gitlab/metrics/web_transaction_spec.rb

@@ -180,11 +180,11 @@ describe Gitlab::Metrics::WebTransaction do
     end
 
     context 'when request goes to ActionController' do
-      let(:request_format) { :html }
+      let(:request) { double(:request, format: double(:format, ref: :html)) }
 
       before do
         klass = double(:klass, name: 'TestController')
-        controller = double(:controller, class: klass, action_name: 'show', request_format: request_format)
+        controller = double(:controller, class: klass, action_name: 'show', request: request)
 
         env['action_controller.instance'] = controller
       end
@@ -195,7 +195,7 @@ describe Gitlab::Metrics::WebTransaction do
       end
 
       context 'when the response content type is not :html' do
-        let(:request_format) { :json }
+        let(:request) { double(:request, format: double(:format, ref: :json)) }
 
         it 'appends the mime type to the transaction action' do
           expect(transaction.labels).to eq({ controller: 'TestController', action: 'show.json' })