fix(sim): Clarify behaviour for same-name sensitive volumes

The transport engines allow registering of multiple nodes
with the same volume/same volume name (copy mechanism).
In `FairRoot` this mechanism works provided unique volume name
over the whole geometry setup of different detectors.

The commit clarifies the situtation:
1. for same volume names in one detector, it quenches the log message
by moving `LOG` and changing it severity
from `LOG(error)` in `FairVolumeList::addVolume()`
to `LOG(debug)` in `FairModule::AddSensitiveVolume()`.
2. for same volume names accross different detectors,
the program prints appropriate `LOG(fatal)`.

Fixes the issue #1595.

fairroot/base/sim/FairModule.cxx

@@ -216,8 +216,6 @@ void FairModule::SetGeometryFileName(TString fname, TString)
 
 void FairModule::RegisterSensitiveVolume(FairVolume& vol)
 {
-    vol.setModId(fModId);
-    vol.SetModule(this);
     fAllSensitiveVolumes.push_back(&vol);
     ++fNbOfSensitiveVol;
 }
@@ -249,7 +247,7 @@ void FairModule::ProcessNodes(TList* nodes)
         std::ignore = node->calcLabTransform();
 
         auto nodeTruncName = node->getTruncName();
-        auto volume = std::make_unique<FairVolume>(nodeTruncName, fNbOfVolumes);
+        auto volume = std::make_unique<FairVolume>(nodeTruncName, fNbOfVolumes, fModId, this);
         volume->setRealName(node->GetName());
 
         auto addedVol = vList->addVolume(std::move(volume));
@@ -280,8 +278,10 @@ void FairModule::AddSensitiveVolume(TGeoVolume* vol)
     auto volName = vol->GetName();
     LOG(debug2) << "AddSensitiveVolume " << volName;
 
-    auto addedVol = vList->addVolume(std::make_unique<FairVolume>(volName, fNbOfVolumes));
+    auto addedVol = vList->addVolume(std::make_unique<FairVolume>(volName, fNbOfVolumes, fModId, this));
     if (!addedVol) {
+        LOG(debug) << "FairModule: Trying to register element " << vol->GetName() << " for detector " << GetName()
+                   << " failed, beacuse it was already defined";
         return;
     }
     ++fNbOfVolumes;

fairroot/base/sim/FairVolumeList.cxx

@@ -12,6 +12,9 @@
 
 #include "FairVolumeList.h"
 
+#include "FairDetector.h"
+#include "FairVolume.h"
+
 FairVolume* FairVolumeList::getVolume(const TString& name)
 {
     auto obj = findObject(name);
@@ -35,8 +38,13 @@ FairVolume* FairVolumeList::addVolume(std::unique_ptr<FairVolume> vol)
     auto vol_found = findObject(vol->GetName());
 
     if (vol_found) {
-        LOG(error) << "FairVolumeList element: " << vol->GetName() << " VolId : " << vol->getVolumeId()
-                   << " already defined " << vol_found->getVolumeId();
+        // FATAL: The same volume name for different detectors
+        if (vol->GetDetector() != vol_found->GetDetector()) {
+            LOG(fatal) << "FairVolumeList Trying to register element: " << vol->GetName()
+                       << " (VolId=" << vol->getVolumeId() << ") for detector " << vol->GetDetector()->GetName()
+                       << ", but it was already defined (VolId=" << vol_found->getVolumeId() << ") for detector "
+                       << vol_found->GetDetector()->GetName();
+        }
         return nullptr;
     }