removes user_id column from User model to use idiomatic Rails automatic IDs

app/models/message.rb

@@ -4,7 +4,7 @@ class Message < ApplicationRecord
   validates_presence_of :creator_id, :receiver_id, :message
 
   def creator_name
-    if creator = User.where(user_id: self.creator_id).first
+    if creator = User.where(id: self.creator_id).first
       creator.full_name
     else
       "Name unavailable"