Is it possible to trigger callback for after_commit rather than after_create or after_save

This might be a suggestion for a future request.

Example from docs:

```
books.each do |book|
  book.run_callbacks(:save) { false }
  book.run_callbacks(:create) { false }
end
```

I'd love to have an option for `commit` as well.

```
book.run_callbacks(:commit)
```

I was wondering why we only got 2 options for callbacks, `save` and `create`? 

Thanks in advance.