new afterTransaction hook

[roggervalf]

it could be great to have a hook to run some async functions only when a transaction succeeds as in a rollback we could not want some methods to be done. A workaround is runAfterTransaction method as described in https://gregberge.com/blog/knex-transactions. The downside of it is that when we await a transaction operation, it doesn't wait for the runAfterTransaction operation, those are going to happen sometime after awaiting the main transaction.