Add favorites to Outlook calendar

[alexiri]

Add favorite events and categories to Outlook calendar.

For favorited categories, only new/updated events are added to the calendar because Indico is missing the signals signals.users.favorite_category_added and signals.users.favorite_category_removed.

Depends on indico/indico#6618

[alexiri]

Regarding the concern of somebody marking Home as favorite, this is actually already an issue for the calendar exporter feature: you can export an ical file for the entire Indico instance. It takes a little while on the CERN instance and produces an ical file with 6114 events (for me, users with more access will probably get more), all ending in the future.

With the code as it's implemented now, marking a category as favorite wouldn't affect that many events because it's no longer fully recursive. Even if it were, though, this may not really be an issue depending on how indico outlook is executed. I had assumed it would be a celery task, but it doesn't look like it is and I can't find how it's triggered nor how often. I think as long as multiple executions aren't allowed to overlap, the impact of a large quantity of updates should be fairly limited.

[ThiefMaster]

Even if it were, though, this may not really be an issue depending on how indico outlook is executed. I had assumed it would be a celery task, but it doesn't look like it is and I can't find how it's triggered nor how often. I think as long as multiple executions aren't allowed to overlap, the impact of a large quantity of updates should be fairly limited.

It is. See outlook/indico_outlook/__init__.py (once every 15 minuts, and yes by default we lock tasks so they do not overlap). And it's not so much about not wanting the task to take long (it's already fairly slow as it is though!), but rather avoiding to accidentally add 100s or 1000s events to someone's calendar.

Regarding the concern of somebody marking Home as favorite, this is actually already an issue for the calendar exporter feature: you can export an ical file for the entire Indico instance. It takes a little while on the CERN instance and produces an ical file with 6114 events (for me, users with more access will probably get more), all ending in the future.

Actually your comment just reminded me of the perfect solution! We have something called visibility. Add a .filter(Event.is_visible_in(favorite_category_id)) to the query for events (unfortunately this does not accept multiple categories, BUT you could possibly use the CTE for visibility information directly - check the code if is_visible_in!). I think visibility check AND access check together may be pretty reasonable to stop people from doing stupid things and flooding their calendar.

[alexiri]

After 4386d9a, this PR now depends on indico/indico#6618.