Easy registration of new accounts

I keep having problems with new users:

1. I add their account.
2. They receive their activation link
3. They don't have time to click on it in that instance
4. The mail moves down in their inbox
5. When they first have to use their account they remember the mail, click on the link and the token is invalid.

What works:

1. I add their account with a password
2. I send them username and password

Problem is: I can't force them to change the password after the first login, can I? That would be a good feature:

1. Add new account with autogenerated one-time-Password
2. Nextcloud sends it directly to the new user