fix(dav): Handle duplicate event reminder #8999

Job	Run time
changes	6s
integration-sqlite (capabilities_features, 8.2, main)	5m 27s
integration-sqlite (collaboration_features, 8.2, main)	1m 52s
integration-sqlite (comments_features, 8.2, main)	1m 19s
integration-sqlite (dav_features, 8.2, main)	4m 20s
integration-sqlite (features, 8.2, main)	10m 38s
integration-sqlite (federation_features, 8.2, main)	2m 17s
integration-sqlite (--tags ~@large files_features, 8.2, main)	6m 12s
integration-sqlite (filesdrop_features, 8.2, main)	57s
integration-sqlite (openldap_features, 8.2, main)	4m 57s
integration-sqlite (openldap_numerical_features, 8.2, main)	5m 31s
integration-sqlite (ldap_features, 8.2, main)	1m 7s
integration-sqlite (remoteapi_features, 8.2, main)	48s
integration-sqlite (setup_features, 8.2, main)	50s
integration-sqlite (sharees_features, 8.2, main)	7m 26s
integration-sqlite (sharing_features, 8.2, main)	15m 20s
integration-sqlite (videoverification_features, 8.2, main)	3m 2s
integration-sqlite-summary	4s
	1h 12m 13s

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