How to ask anonymous to confirm their flag by email? I need to add Flags to one of my content types. Two kinds, actually:


I'll take care of it
Solved


Second flag should be available only to node author, and only if first one was already raised. But that's simple part. First kind of flag is trivial for logged in users, too.

The point is - I need to make first kind of flag available for anonymous users, too. And I need to make sure I have their valid email addresses. Standard confirmation link in mail would be OK - so how do I do that?

I know I can develop custom module from scratch, and I will if needed, but I was sure there is already a out-of-the-box solution, and I simply can't find it now.

Just to make some things clear:


Flag module works for anonymous users if you install Session API. No problem here.
I planned to keep emails in Email Field attached to flag itself. For logged in users it defaults to their email, and if they decide to change it, so be it, I have a way to reach them anyway. For anonymous, I want it verified by link in email, and if it is not verified in time, I want to delete flag. Deletion will be easy with CRON and Rules or simple helper module, it's verification that's complicated (and I hope solved already).
I would use hook_flag_link_type_info() to provide a link type like the 'confirm' link type provided by the flag module. Copy their approach, but on the 'confirm' form you ask for the users e-mail address (if the user is anonymous). You save the value to the email field you added to your flag and the Rules module should be able to do the rest for you. It requires a bit of custom code (not too much I would guess), but the major part of the functionality (flagging, unflagging, rules integration, ...) still comes from the Flag module.

[EDIT] For the verification part: Add a boolean field to your flag ('Verified') which you change with the verification link you send by mail. The "Solved" flag can be hidden/shown with hook_flag_access().