Bug 1250189 contains an initial proposal for a "batch upload" API for sync. However, the terminology used there was causing a little confusion about whether the word "batch" refers to a single part of a larger transaction, or the overall set of items spanning several requests. I still hope we can come up with an API that doesn't cause such confusion, so I'm spinning off a concrete sub-bug to track that work.

We've done all the bikeshedding we're every likely to do, final result in https://github.com/mozilla-services/docs/pull/60