fix(dav): Handle duplicate event reminder #8977

Job	Run time
changes	5s
integration-sqlite (capabilities_features, 8.2, main)	5m 18s
integration-sqlite (collaboration_features, 8.2, main)	6m 25s
integration-sqlite (comments_features, 8.2, main)	5m 29s
integration-sqlite (dav_features, 8.2, main)	8m 34s
integration-sqlite (features, 8.2, main)	11m 1s
integration-sqlite (federation_features, 8.2, main)	7m 23s
integration-sqlite (--tags ~@large files_features, 8.2, main)	12m 13s
integration-sqlite (filesdrop_features, 8.2, main)	5m 16s
integration-sqlite (openldap_features, 8.2, main)	5m 30s
integration-sqlite (openldap_numerical_features, 8.2, main)	5m 17s
integration-sqlite (ldap_features, 8.2, main)	5m 14s
integration-sqlite (remoteapi_features, 8.2, main)	5m 21s
integration-sqlite (setup_features, 8.2, main)	4m 7s
integration-sqlite (sharees_features, 8.2, main)	6m 49s
integration-sqlite (sharing_features, 8.2, main)	19m 46s
integration-sqlite (videoverification_features, 8.2, main)	8m 11s
integration-sqlite-summary	4s
	2h 2m 3s

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