Make Relation.insertAll atomic

[srfc]

Issue

Relation.insertAll is not atomic at the moment. We have opened another issue to add a return type indicating success or failure, but this issue relates to the ability to roll back all singular inserts should one of them fail.

Problem Description

• If one insert of a Relation.insertAll fails, you get a state of the Relation that is unknown to the developer. The Relation itself should support atomic insertAlls.

Supporting Information

• See discussion:

Regarding insertAll, I'm totally fine with also changing its return type to Try[Seq[Record]], but then we should make clear its semantics. I would prefer it to be an atomic operation (this will need some more logic, but should be possible).