Spec response for forgery (#3248)

Remove protect_from_forgery in ApiController, which is disabled by the
following skip_before_action, as well.

spec/controllers/api_controller_spec.rb

@@ -0,0 +1,18 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+describe ApiController, type: :controller do
+  controller do
+    def success
+      head 200
+    end
+  end
+
+  it 'does not protect from forgery' do
+    ActionController::Base.allow_forgery_protection = true
+    routes.draw { post 'success' => 'api#success' }
+    post 'success'
+    expect(response).to have_http_status(:success)
+  end
+end