Automatic merge from submit-queue
Expose Changesets (transactions) in dns provider
This makes the dnsprovider usable in more scenarios, and it also solves
some TODOs in the federation code.
WIP - I'm going to test this to make sure this both works and is sufficient for use in my dns controller, but I wanted to put some code behind the talk in #28477. cc @quinton-hoole
Issue #28477