\OCA\Calendar\Service\Appointments\BookingCalendarWriter depends on Sabre

[ChristophWurst]

Expected behavior

Our app only uses its own code, or directly dependent libraries

Actual behavior

Server's 3rdparty library is used

Possible solution

• Ship another lib for the same purpose
• Ship our own, scoped version of Sabre

Calendar app

Calendar app version: v3

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cc @miaulalala

additional code from #5339 needs refactoring too.

[tcitworld]

We could even generate the whole ICS ourselves manually as there's nothing special about it, and no logic to apply, only injecting variables in a template.

[miaulalala]

Unless it's linebreaks - any ideas on how to correctly handle a long description? Or special chars possibly like emojis? We'd have to filter those I guess.

[tcitworld]

Description should be handled with
https://github.com/sabre-io/vobject/blob/0a2e27c797ec0934f376764e1a16567bbbcece0b/lib/Property/Text.php#L261-L272

The rest is UTF8 :)
https://datatracker.ietf.org/doc/html/rfc5545#section-3.1.4