This Dockerfile allows building a given repo and branch of titan.core.git which can then be used by any ttcn-*-test/ environment by simply changing its Dockerfile "FROM" line from $REGISTRY/$USER/debian-bullseye-titan to $REGISTRY/$USER/debian-bullseye-titan-mater.
This is useful to debug or develop titan.core or test whether a given testsuite works fine with a newer version of titan.core.
