Implement unsubscribe route to delete subscriptions

app/policies/subscription_policy.rb

@@ -2,4 +2,17 @@ class SubscriptionPolicy < ApplicationPolicy
   def create?
     everyone
   end
+
+  def destroy?
+    author? || admin?
+  end
+
+  def show_error?
+    everyone
+  end
+
+  def author?
+    @user == @record.user
+  end
+  private :author?
 end