Database example for invitations.
It should at least contain these fields:
User name (PubPub)
Not responding: the user has not responded to the invitation email
Responded: the user has already responded to the invitation email
Problem: the user has had a problem registering on the platform, etc.
Ready: you have already registered on the platform and sent your email
Not integrated: it is pending to include the user in the corresponding Pub or Community
Problem: the computer has had a problem finding the user
Done: the user is already added to the corresponding Pub or Community