Repeating Tasks not working with multiple outlook clients

[meichthys]

@aluxnimm I've closed #327 in favor of this issue since that one was getting too confusing.

Our Use Case

We are trying to sync a few outlook clients to the same task list, but repeating tasks are not synced properly.

How to reproduce

Note: For reproducibility I have turned off auto sync and "Sync after change" in the Caldavsynchronizer settings.

1. Setup two instances (A and B) of outlook to sync to the same remote (I'm using Nextcloud) task list. Alternatively just setup one instance to sync to a task list, then copy the profile (be sure to change the local task list so the two profiles are not syncing to the same local task list).
2. In instance A, create a task that repeats daily with no end date.
3. Manually Sync instance A
4. Manually Sync instance B and verify that the task shows - it will show as a normal task (not a repeating task)
5. In instance B, mark the task as completed then sync
6. In instance A, sync to show completed task. Instance A will then re-create the task
7. Manually sync instance A
8. Manually sync Instance B to see the newly created task <- this is where the issue starts since the newly created task will have the wrong date and will already be marked as completed while Instance A still shows the newly created task as incomplete.

Note: manually making a change to the newly created repeating task in instance A seems to fix things.

See the screen recording for a full reproduction of the issue. It appears to me that all that would be needed to fix this is to automatically make a small change to the newly created repeating task in step 6 above. Would this be possible to implement?

Currently the state of repeating tasks is quite broken if syncing between multiple profiles or instances of outlook. We've seen situations where the task will keep duplicating after each sync, and situations where a daily task gets changed to a weekly task. (See #327 for more details)

screen recording.zip