Decide on DOI minting behavior when save fails

[barmintor]

The publish actions in Hyc3 assume a DOI has been minted - currently in the save action/behavior. How should that mint be handled in the event of a failed save?

Quoting @elohanlon's review:

If something goes wrong during the save, the digital object's doi field will be reverted properly because of the existing code below, but I think the DOI will still exist indefinitely in a reserved state in the external DOI system.

And @barmintor's response:

I'm not sure what to do about this. Send the UID with the DOI mint metadata? Reluctant to rely on sending a withdrawal since we'd already be in an error state. We could have a pending DOI and do the mint after the save?