Make engine routes just prepend to apps routes instead of creating engine routes

This makes things a bit simpler in terms of routing, we avoid a problem running specs and we can still have the engine routes separated in specific files

config/routes.rb

@@ -89,11 +89,6 @@ Openfoodnetwork::Application.routes.draw do
 
   get 'sitemap.xml', to: 'sitemap#index', defaults: { format: 'xml' }
 
-  # Mount engine routes
-  mount Web::Engine, :at => '/'
-  mount Catalog::Engine, :at => '/'
-  mount OrderManagement::Engine, :at => '/'
-
   # Mount Spree's routes
   mount Spree::Core::Engine, :at => '/'
 end

engines/order_management/config/routes.rb

@@ -1,5 +1,5 @@
-Spree::Core::Engine.routes.prepend do
-  namespace :admin do
+Openfoodnetwork::Application.routes.prepend do
+  namespace :order_management do
     namespace :reports do
       resource :enterprise_fee_summary, only: [:new, :create]
     end

engines/web/config/routes.rb

@@ -1,4 +1,4 @@
-Web::Engine.routes.draw do
+Openfoodnetwork::Application.routes.prepend do
   namespace :api do
     scope '/cookies' do
       resource :consent, only: [:show, :create, :destroy], controller: "cookies_consent"