feat(museum): create Museum.title_with_city and use it in the view.

related: #2

cubicweb_tuto/entities.py

@@ -16,3 +16,14 @@
 # along with this program. If not, see <http://www.gnu.org/licenses/>.
 
 """cubicweb-tuto entity's classes"""
+from cubicweb.entities import AnyEntity, fetch_config
+
+
+class Museum(AnyEntity):
+    __regid__ = "Museum"
+
+    fetch_attrs, cw_fetch_order = fetch_config(["name"])
+
+    @property
+    def title_with_city(self):
+        return f"{self.name} ({self.is_in[0].name})"

cubicweb_tuto/views.py

@@ -27,5 +27,4 @@ class MuseumPrimaryView(PrimaryView):
         """Renders the entity title, by default using entity's
         :meth:`dc_title()` method.
         """
-        city_name = entity.is_in[0].name
-        self.w(f"<h1>{entity.name} ({city_name})</h1>")
+        self.w(f"<h1>{entity.title_with_city}</h1>")