Investigate TransactionManager using Kotlin suspend DSL

[nomisRev]

We should add a TransactionManager with following signatures, but ideally it should work through a Kotlin suspend DSL.

Idea:

manager.transaction {

  // abort(), if aborted it doesn't commit
} // auto-commit, if lambda successfully worked without a call to `abort()`

Should be possible to install some listeners to manager.

manager.onComplete { didComplete: Boolean -> }