calling methods that trigger callbacks can cause `after_commit` callbacks to run multiple times

If an `after_commit` is called inside of a transaction and that transaction has calls to model methods that can trigger model callbacks, the block passed to `after_commit` will be called multiple times. For example,

```ruby
ActiveRecord::Base.transaction do
User.create!(email:)
ev = Event.create!(name: 'created user', source: 'admin')

after_commit do
send_welcome_email!
end

track_event!(ev)
end
```

When this transaction runs, the welcome e-mail will be sent multiple times because the block is run repeatedly.