Sharing of Draft Registrations Between users outside of the same account or users without an account

Users want to be able to share a draft registration prior to paying for the registration so someone else can confirm that the information in the registration is correct.

The issue does not name any files, tests, or entry points. Start by locating the draft registration workflow and its existing ownership and access rules, then determine the sharing flow and confirmation boundary. Done means a draft can be reviewed by another user or someone without an account before payment, with access handled appropriately.

Written by the indexing model from the issue text.