extract_relevant_calendar_appointment_shortname

[bensteUEM]

https://github.com/bensteUEM/ChurchWebHelper/blob/fcea2f5d8c2cd2daaf870cd8f25192487ccf993f/church_web_helper/helper.py#L45

[bensteUEM]

https://forum.church.tools/topic/11586/r%C3%BCckfrage-zu-calendars-appointments-rtypes

[bensteUEM]

• remove interface workaround if type definition is updated by CT team