Error building backend image (tests fail in gradle build process)

### Current Behavior
During the build process of the backend image gradle fails with a test error:
TransferApiEndToEndTest > initializationError FAILED
org.testcontainers.containers.ContainerLaunchException at TransferApiEndToEndTest.java:40
Caused by: org.rnorth.ducttape.RetryCountExceededException at TransferApiEndToEndTest.java:40
Caused by: org.testcontainers.containers.ContainerLaunchException at TransferApiEndToEndTest.java:40
Caused by: com.github.dockerjava.api.exception.InternalServerErrorException at TransferApiEndToEndTest.java:40

So the build of the image fails and the whole mxd does not work.

### Expected Behavior
Expected behavior: No error in the backend build process

### Steps To Reproduce
using openjdk-21 on ubuntu 24.01.1
followed the gradlew command as in the README.md