2 Hour offset on mouting actions endpoint when database is in CEST

When we set the TZ: Europe/Berlin env variable for the database container (as UFZ staging has), then we have on offset for the result of the mounting actions endpoint.

Steps to reproduce:

set the TZ variable for the backend container
restart the docker compose (& maybe clean the existing volumes for the services)
add a device
add a configuration
mount a device at 12:00 (utc)
query for the mounting actions for 12:00 (utc) => no device mounted
query for the mounting actions on 14:01 (utc) => device is mounted