fix: improve built-in grid renderer logic

- add `render_batch_id()`
- allow kwargs for `render_currency()`
- caller may specify built-in renderer w/ string identifier

tests/grids/test_base.py

@@ -208,6 +208,11 @@ class TestGrid(WebTestCase):
         self.assertIsNot(grid.renderers['foo'], render2)
         self.assertEqual(grid.renderers['foo'](None, None, None), 42)
 
+        # can use built-in string shortcut
+        grid.set_renderer('foo', 'quantity')
+        obj = MagicMock(foo=42.00)
+        self.assertEqual(grid.renderers['foo'](obj, 'foo', 42.00), '42')
+
     def test_set_default_renderer(self):
         model = self.app.model
 
@@ -1343,6 +1348,17 @@ class TestGrid(WebTestCase):
     # rendering methods
     ##############################
 
+    def test_render_batch_id(self):
+        grid = self.make_grid(columns=['foo', 'bar'])
+
+        # null
+        obj = MagicMock(foo=None)
+        self.assertEqual(grid.render_batch_id(obj, 'foo', None), "")
+
+        # int
+        obj = MagicMock(foo=42)
+        self.assertEqual(grid.render_batch_id(obj, 'foo', 42), "00000042")
+
     def test_render_boolean(self):
         grid = self.make_grid(columns=['foo', 'bar'])