The reminder on calendar events is not synchronized

The reminder of an event is not synchronized both for events created on the client and for those created on the server.

Steps to reproduce:

• create a calendar event with reminders on the server
• synchronize with CalDAV client (both Android and Apple)
• create an event on the client with reminders
• synchronize via CalDAV

Expected behaviour:

• synchronized events always have reminders

Actual behaviour:

• synchronized events do not have the reminder configured