CalDAV: handle email aliases for users

[miaulalala]

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Is your feature request related to a problem? Please describe. Currently, email aliases are not considered when processing a scheduling event in CalDAV. A user anna@nextcloud.com might be invited to an event, but the reply could come from anna.larch@nextcloud.com, which is functionally the same email address; nonetheless the user will be considered a party crasher and the original ATTTENDEE will never have its PARTSTAT updated.

This is especially problematic for iMIP messages, as the email addresses are the primary means of identifying the replying user.

Describe the solution you'd like CalDAV should have a way to access email aliases for users. A way to do this could be to create a specific service that accesses and compares email adresses to whatever a VEVENT has stored in the ATTENDEE / ORGANIZER property.

Describe alternatives you've considered

Additional context Follow up to https://github.com/nextcloud/server/pull/40876

[tcitworld]

Is this the same as https://github.com/nextcloud/calendar/issues/4918 ? Might be fixed by https://github.com/nextcloud/server/pull/31029

[miaulalala]

ah nice, didn't see that. I will check if that works. Thanks Thomas!

[juliusknorr]

While I'm not sure if this was scope of the initial issue report, but seems close enough to not open a separate one:

After my name change my primary email to julius.knorr also changed on our instance, still having an alias for my old email address.

• I've added my old email julius.haertl as additional email address to my nextcloud profile.
• When I receive a calendar invite to that email address I do not see it in the calendar, this only works with the primary email

[fcharlaix-opendsi]

We have encountered this problem recently, our internal documentation says to accept with Nextcloud and not the built-in Thunderbird action to avoid conflict with already created event not already synced to Thunderbird.

Since we have a second email domain alias we encounter strange missing events, I got one on my secondary address and done some tests, despite adding addition emails to my Nextcloud profile this sandy don't work.