A failure to commit a reactive transaction will complete the
transaction and clean up resources. Executing a rollback at
that point is invalid, which causes an
IllegalTransactionStateException that masks the cause of the
commit failure.
This change restructures TransactionalOperatorImpl and
ReactiveTransactionSupport to avoid executing a rollback after
a failed commit. While there, the Mono transaction handling in
TransactionalOperator is simplified by moving it to a default
method on the interface.
Closes gh-27572
edf0ae77e5