Set up Grape API v3

app/api/api.rb

@@ -0,0 +1,7 @@
+class API < Grape::API
+  format :json
+
+  get '/' do
+    "I work!"
+  end
+end

config/application.rb

@@ -138,6 +138,10 @@ module OpenProject
       ActionMailer::Base.view_paths = ActionView::PathSet.new(ActionMailer::Base.view_paths.to_ary.reverse)
     end
 
+    # Load API files
+    config.paths.add File.join('app', 'api'), glob: File.join('**', '*.rb')
+    config.autoload_paths += Dir[Rails.root.join('app', 'api', '*')]
+
     OpenProject::Configuration.configure_cache(config)
   end
 end

config/routes.rb

@@ -117,6 +117,8 @@ OpenProject::Application.routes.draw do
     end
   end
 
+  mount API => '/api/v3'
+
   match '/roles/workflow/:id/:role_id/:type_id' => 'roles#workflow'
   match '/help/:ctrl/:page' => 'help#index'