Handling of recurrence rules in time-ranged requests

Description: When requesting a set of conferences (GET /conferences) within a specific time range, only the first event in the list of all recurrences is regarded.

How to reproduce: Create a conference with a daily recurrence schedule and date the first event to yesterday.

Expected Behavior: The first sequel of the conference should show up beneath "Heutige Konferenzen"

Actual Bahavior: The conference does not show up beneath "Heutige Konferenzen"