Implement unsubscribe route to delete subscriptions

config/locales/de.yml

@@ -630,4 +630,7 @@ de:
   comments:
     deleted: "Gelöscht"
     save_update: "Speichern"
+  subscriptions:
+    successfully_unsubscribed: "Ihr Abonnement für weitere Kommentare auf dieser Kommentaranfrage wurde erfolgreich beendet."
+    subscription_not_existent: "Das Abonnement, von dem Sie sich abmelden wollen, existiert nicht."
 

config/locales/en.yml

@@ -651,3 +651,6 @@ en:
   comments:
     deleted: "Deleted"
     save_update: "Save"
+  subscriptions:
+    successfully_unsubscribed: "You successfully unsubscribed from this Request for Comment"
+    subscription_not_existent: "The subscription you want to unsubscribe from does not exist."

config/routes.rb

@@ -21,7 +21,11 @@ Rails.application.routes.draw do
   delete '/comment_by_id', to: 'comments#destroy_by_id'
   put '/comments', to: 'comments#update'
 
-  resources :subscriptions
+  resources :subscriptions do
+    member do
+      get :unsubscribe, to: 'subscriptions#destroy'
+    end
+  end
 
   root to: 'application#welcome'