We've seen users provide broken arguments, such as:

> [1] crane transform --optional-flags="add-annotations=migration_using_crane:true"

This should have been

--optional-flags="add-annotations=migration_using_crane=true"

It would be very useful to extend our plugin API/protocol to allow for plugin authors to optionally validate their inputs so that they could pass back warnings/errors/ or other informational messages.

We probably want this to happen prior to the transforms actually taking place. Questions to consider: if any plugins error, do we stop the entire operation, or should we still continue with those that didn't error?

Let's write up an enhancement and get this implemented post-GA.