Add tests & factories for UserMute feature

test/factories/messages.rb

@@ -14,5 +14,9 @@ FactoryBot.define do
     trait :read do
       message_read { true }
     end
+
+    trait :muted do
+      muted { true }
+    end
   end
 end

test/factories/user_mute.rb

@@ -0,0 +1,6 @@
+FactoryBot.define do
+  factory :user_mute do
+    owner :factory => :user
+    subject :factory => :user
+  end
+end