Depends on D19923. Ref T11351. Currently, this transaction takes an `Image` as the `newValue` and uses some magic to reduce it into PHIDs by the time we're done.
This creates some problems today where I'd like to get rid of `willApplyTransactions` for MFA code. In the future, it creates a problem becuase there's no way to pass an entire `Image` object over the API.
Instead, create the `Image` first, then just provide the PHID. This is generally simpler, will work well with the API in the future, and stops us from needing any `willApplyTransaction` stuff.