This is the 1st followup of [!56242 (merged)]
Since in that one we finally avoid creating everything const.
Now we are able to actually "manipulate" things without const_cast for a change ...
One has to look only on the following commit and any commits after that one until the previous MR is merged (ATLAS-EGamma/athena@cb90a633)
The true purpose / magic is the TrackingVolumeManipulator
[https://gitlab.cern.ch/ATLAS-EGamma/athena/-/blob/cb90a633d968213901ee12e75213da5bdfca920e/Tracking/TrkDetDescr/TrkGeometry/src/TrackingVolumeManipulator.cxx]
that now becomes THREAD_SAFE
ping @fwinkl
There are one "syntactical" question I had on combining span and shared_ptr etc ...
[ATLAS-EGamma/athena@cb90a633]
ping @ssnyder
with whom I discussed them.
A mock perhaps easier to parse .
[https://godbolt.org/z/MdzEjaYMG] (scroll around line 500)