Right now sampling happens on startTransaction for Java, .NET, Python, and probably the others too.

The problem I see here is, a transaction.status could be set at a later point if an error has occurred.

I'd like to use the status to properly sample my transactions, I'd like higher sampling if there's an error.
This is not possible right now as it's being sampled or not already in the startTransaction and status might not be available, yet.

A possible solution would be to sample only on finish when the transaction should have its full payload.

cc @rhcarvalho @bruno-garcia @Tyrrrz @maciejwalkowiak @HazAT @brustolin