various cleanups
A few classes have setters that are not really needed. Immutability should be treasured, so I propose to remove them.
Edited by Martin Reinecke
All shared GitLab runners will switch from Python 3.9 to 3.12 as default image the next days.
A few classes have setters that are not really needed. Immutability should be treasured, so I propose to remove them.