Two migrations for users_apps_properties table

Just started with a couple of migrations. I am not sure if the 2nd migration was needed (I replaced column property_key_type_id with add_reference, but the end results in schema.rb appear to be the same)?

Also, for both fields that I added, I created indexes. All previously created foreign keys don't have indexes defined. This might be not so important for POC, but for the future app - do we need to define indexes in our schema for the foreign keys?