This web API should be able to trigger backfills & retriggers on Taskcluster.
It's highly dependent on the actual backend mechanism for doing these operations.
There's a frontend library called taskcluster-client for doing these operations. Don't yet know if there's a backend library as well.
Work on this ticket could uncover some changes needed for bug 1571364. It's possible we'll need the classes behind that tool to provide extra context.