Do not delete scheduled events in the past when modifying capture agents for rooms

**Version**
3.25

**Describe the bug**
When modifying capture agents for rooms in the admin settings, all scheduled events are changed and propagated to Opencast. This does include past events, which will break the index in Opencast.

Instead, only events in the future should be ever touched. Additionally, the for modifying the capture agents and workflows is quirky and needs to be reworked.