[dev] User invitation / e-mail verification module

[Luciano Ramalho]

Hello, are there Horde app modules that do either one of these related 
tasks?

- allow a user to type (external) e-mail addresses and have invitations 
to join the site sent to them (like Linkedin does)

- send an automated e-mail message with a token to a user to verify his 
address, and then mark the address as verified once the user clicks on a 
link (like mailman does)

I understand most Horde installations don't have open sign-up, but I 
need something along those lines for Groo.

If no such code exists, I'll contribute it.

Cheers,

Luciano

PS. If a PEAR module exists to do something like that, it would be nice 
too. I could not find one.