Not merging contacts when creating an event from Android

[DavidMndz]

Steps to reproduce

1. Configure replication between Android calendar and Nextcloud Calendar.
2. Create a user in Nextcloud, including the mail address.
3. In Android, create an event in the Nextcloud Calendar, getting it replicated to Nextcloud through DAVx5. In the event invite the contact you already created, using the mail address defined in the Nextcloud user profile.
4. Save the event and let the replication works.

Expected behaviour

The event should recognize the user in Nextcloud and consider it as "Nextcloud user", not an external user by mail.

Actual behaviour

The user invited is the email address put in the Android side, but not merged with the Nextcloud user.

Calendar app

Calendar app version: 2.3.0

CalDAV-clients used: DAVx5

[tcitworld]

I think we already had such an issue.

Related to #3101 anyway