group subscription emails fail for multiple groups

the mailing subscription email process seems to be flawed. not sure if this is a recent bug or just general problems with the handling. here is how you reproduce:

1) create several groups marked publicly visible
2) create a profile that includes the groups field
3) expose the profile in create view and complete it – selecting several of the groups

after submission, the user receives an email for each of the groups selected, to confirm the requests. click the link in the first email to confirm subscription. this redirects you to the website and acts as expected.

now go to the second email and click the link. it redirects you to the website and appears to confirm the group, but the name of the group is not included in the confirmation page and the group remains in pending status in the user's record. the same is found of any other emails received and replied to.

the immediate issue is that the links apparently are not group-contact specific, or perhaps there's something in the confirmation code that ignores a contact that has already confirmed one group.

however – I think a better handling would be to send one email listing all groups the user selected, and provide one page where all of them can be confirmed in a single step – rather than sending one email per group.

regardless of the solution – in the current state, it's impossible for a user to confirm more than one group on their record. the first may be confirmed, but all subsequent ones are ignored and left in pending state.