ArMem: Revice get/find interface

source/RobotAPI/libraries/armem/core/base/detail/MemoryContainerBase.h

@@ -108,6 +108,15 @@ namespace armarx::armem::base::detail
             return _container;
         }
 
+        DerivedT& _derived()
+        {
+            return static_cast<DerivedT&>(*this);
+        }
+        const DerivedT& _derived() const
+        {
+            return static_cast<DerivedT&>(*this);
+        }
+
 
         /**
          * @throw `armem::error::ContainerNameMismatch` if `gottenName` does not match `actualName`.
@@ -123,6 +132,19 @@ namespace armarx::armem::base::detail
         }
 
 
+        template <class ChildT, class KeyT, class ...ChildArgs>
+        ChildT& _addChild(const KeyT& key, ChildArgs... childArgs)
+        {
+            auto [it, inserted] = this->_container.try_emplace(key, childArgs...);
+            if (not inserted)
+            {
+                throw armem::error::ContainerEntryAlreadyExists(
+                    ChildT::getLevelName(), key, DerivedT::getLevelName(), this->_derived().name());
+            }
+            return it->second;
+        }
+
+
     protected:
 
         mutable ContainerT _container;