Send welcome email

[manast]

When a user is created, optionally, we should send a welcome email with a link to reset the password. For example, when creating new users with the dashboard, the new users are created without a password (for security), but then the new user will not be able to login until it resets its password. It would be simpler if the users just get an onboarding email so that they can reset the passwords just by clicking a link and then login for the first time.