No email sent when eventsignup POST contains accepted:true

Created by: temparus

An admin can always provide the accepted field for an eventsignup set to true.

If one does so with a POST request, no email is sent to the person who was signed up by the admin.

Expected behavior would be that the signed up person also gets the email that they were signed up. Otherwise, the user might not know that he/she is on the participants list of that event.