Poolboy should notify workers when they are returned to the pool

[asabil]

When working with a database such as postgresql, the workers owning the connection need to be notified when returned to the pool in order to give the worker the opportunity to reset the state of the connection (rollback pending transactions for example).

[bullno1]

👍

[juhlig]

Yeah, this is just what I'm wishing for right now. Maybe an (optional) callback in poolboy_worker would be the best thing to do, which would be called on checkin. The same could be done for checkout, though this would probably be of little use.

[juhlig]

Or a function to call that could be given as a pool arg.