If installed along with `auth_signup`, it sends an email when creating a missing user authenticated through LDAP.
It is a confusing message that makes no sense, because the user is, from his POV, not actually creating a new user, but just authenticating with a new app with his known company-wide credentials.
Besides, that invitation leads the user to change his password in Odoo, although he probably doesn't want to do that and have a password for Odoo and another in the LDAP server.
The best option is to disable that email completely, which is what this commit does.
closesodoo/odoo#29243