I'm using uuid v7 for the invite_key because the AdminInvite model supports soft deletes with a unique constraint to retain the invite id in the users model while hiding "deleted" invites.

I spent way too long deciding on the invite_key format, and prepended it with `a_` to denote it's admin generated in case we allow user invites in the future and need to differentiate due to other constraints (like closed registration, user invites won't work, but admin invites will)