Add <once-button> for sending email preview; various other tweaks

tailbone/views/master.py

@@ -3280,6 +3280,7 @@ class MasterView(View):
             'readonly': self.viewing,
             'model_class': getattr(self, 'model_row_class', None),
             'action_url': self.request.current_route_url(_query=None),
+            'use_buefy': self.get_use_buefy(),
         }
         if self.creating:
             kwargs.setdefault('cancel_url', self.request.get_referrer())