Route calendar invitations to the calendar associated with the recipient address
Currently, all incoming calendar invitations are added to the default calendar, regardless of which email address they were sent to.
Requested behaviour: Allow users to configure, per email address, which calendar should receive invitations sent to that address. This setting should live at the mailbox/identity level (e.g. in account settings under each address).
Use case: A user with a personal address (e.g. user@proton.me) and a custom-domain business address maintains separate personal and work calendars. Invitations sent to the personal address should land in the personal calendar; invitations sent to the business address should land in the work calendar — without manual intervention.