Assigning a collection of attachments appends to the collection as it did in 5.2. Existing 5.2 apps that rely on this behavior will no longer break when they're upgraded to 6.0.
For Apps generated on 6.0, assigning replaces the existing attachments in the collection. #attach should be used to add new attachments to the collection without removing existing ones.

Add support to startless ranges (e.g. ..10 and ..Date.today), introduced by Ruby 2.7.0-preview1, to Active Record queries. This enables expression like Order.where(created_at: ..1.year.ago).

When the users click the SMS link, their messaging app opens with the phone number and optional message body set in the link.

The class ActiveRecord::QueryAborted makes it possible, for example, to rescue all possible query timeouts without rescuing other query exceptions.

This allows the generator for 6.0 to behave like it used to in 5.2, and overwrite files.