fix: override iTip Broker to fix several issues

[SebastianKrupinski]

Summary

This over rides the iTip broker and the main iTip message generation routine to fix several issues.

• fixes: iTip messages not being generated for certain changes (Summary, Description, Location) changed events should send email calendar#6024
• fixes: Cancel iTip message not being generate when event status is set to cancel Cancelling an event via Status Dropdown doesn't send iMIP CANCEL request #46719
• fixes: Cancel iTip email not being generated when canceling a recurring event after the first occurrence. [Bug] (CalDav): Last occurrence date is not calculated properly on recurring events #45489

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Backports requested where applicable (ex: critical bugfixes)

[ChristophWurst]

Code looks good

Do you have instructions for us for some manual testing? Would it make sense to cover some of this with unit tests? parseEventForOrganizer appears to be free of side effects - event info in, messages out - something that's naturally nice to write tests for.

[SebastianKrupinski]

Code looks good

Do you have instructions for us for some manual testing? Would it make sense to cover some of this with unit tests? parseEventForOrganizer appears to be free of side effects - event info in, messages out - something that's naturally nice to write tests for.

Morning, Sure I can write some test, for it, I originally skipped the tests because iTip broker message generation is already covered by most of our unit tests, but I'll write some test specifically for this, this week.

[SebastianKrupinski]

Do you have instructions for us for some manual testing?

For this, basically just run through the common actions a user would do while inviting an attendee,

1. create an event with attendees
2. update an event (location, description)
3. cancel an event using status in the side bar

And basically see if the attendees received and email.

[ChristophWurst]

Merci for the test coverage 🙏

[SebastianKrupinski]

@ChristophWurst backport to 30 or further? We would need to backport the sabre patch to go further.

[ChristophWurst]

@ChristophWurst backport to 30 or further? We would need to backport the sabre patch to go further.

nextcloud/3rdparty#1939 looks low risk. I'm okay with backporting this further than 30. 28-30 is our current support range: https://github.com/nextcloud/server/wiki/Maintenance-and-Release-Schedule

[SebastianKrupinski]

/backport to stable30

[SebastianKrupinski]

/backport to stable29

[SebastianKrupinski]

/backport to stable28