With a little help, we now have VerseKey

Went with a basic wrapper that cxx is able to handle for the bridge
between the languages, along with simple wrapper methods

src/cxx/module.cc

@@ -15,6 +15,16 @@ namespace sword_rs {
         return rust::String(this->module->getType());
     }
 
+    VerseKey* Module::get_verse_key() const {
+        sword::VerseKey* key = dynamic_cast<sword::VerseKey*>(this->module->getKey());
+        if (key) {
+            // Create a borrowed VerseKey on the heap - caller must delete but not the inner ptr
+            VerseKey* result = new VerseKey{key, false};
+            return result;
+        }
+        return nullptr;
+    }
+
     void Module::increment() {
         this->module->increment();
     }