Assembly: Solver message taskbox. UI setup, App not implemented yet. (#23420)

* Assembly: Solver message taskbox. UI setup, App not implemented yet.

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Update TaskAssemblyMessages.cpp

* Update ViewProviderAssembly.cpp

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

src/Mod/Assembly/App/AssemblyLink.cpp

@@ -541,7 +541,7 @@ AssemblyObject* AssemblyLink::getParentAssembly() const
     return nullptr;
 }
 
-bool AssemblyLink::isRigid()
+bool AssemblyLink::isRigid() const
 {
     auto* prop = dynamic_cast<App::PropertyBool*>(getPropertyByName("Rigid"));
     if (!prop) {
@@ -559,3 +559,18 @@ std::vector<App::DocumentObject*> AssemblyLink::getJoints()
     }
     return jointGroup->getJoints();
 }
+
+bool AssemblyLink::allowDuplicateLabel() const
+{
+    return true;
+}
+
+int AssemblyLink::numberOfComponents() const
+{
+    return isRigid() ? 1 : getLinkedAssembly()->numberOfComponents();
+}
+
+bool AssemblyLink::isEmpty() const
+{
+    return numberOfComponents() == 0;
+}