fix: include grid filters for all column properties of model class

by default anyway.  previous logic started from `grid.columns` and
then only included column properties, but now we start from the model
class itself and let sa-utils figure out the default list

tests/grids/test_base.py

@@ -982,6 +982,17 @@ class TestGrid(WebTestCase):
         self.assertEqual(filters['value'], 42)
         self.assertEqual(myfilters['value'], 42)
 
+        # filters for all *true* columns by default, despite grid.columns
+        with patch.object(mod.Grid, 'make_filter'):
+            # nb. filters are MagicMock instances
+            grid = self.make_grid(model_class=model.User,
+                                  columns=['username', 'person'])
+            filters = grid.make_backend_filters()
+            self.assertIn('username', filters)
+            self.assertIn('active', filters)
+            # nb. relationship not included by default
+            self.assertNotIn('person', filters)
+
     def test_make_filter(self):
         model = self.app.model