feat: add basic batch feature, data model and partial handler

hopefully data model is complete enough for now, but handler does not
yet have all methods, e.g. execute()

tests/test_batch.py

@@ -0,0 +1,70 @@
+# -*- coding: utf-8; -*-
+
+from wuttjamaican import batch as mod
+
+try:
+    import sqlalchemy as sa
+    from wuttjamaican.db import model
+    from wuttjamaican.testing import DataTestCase
+except ImportError:
+    pass
+else:
+
+    class MockBatch(model.BatchMixin, model.Base):
+        __tablename__ = 'testing_batch_mock'
+
+    class MockBatchRow(model.BatchRowMixin, model.Base):
+        __tablename__ = 'testing_batch_mock_row'
+        __batch_class__ = MockBatch
+
+    class MockBatchHandler(mod.BatchHandler):
+        model_class = MockBatch
+
+    class TestBatchHandler(DataTestCase):
+
+        def make_handler(self, **kwargs):
+            return MockBatchHandler(self.config, **kwargs)
+
+        def test_model_class(self):
+            handler = mod.BatchHandler(self.config)
+            self.assertRaises(NotImplementedError, getattr, handler, 'model_class')
+
+        def test_make_batch(self):
+            handler = self.make_handler()
+            batch = handler.make_batch(self.session)
+            self.assertIsInstance(batch, MockBatch)
+
+        def test_consume_batch_id(self):
+            handler = self.make_handler()
+
+            first = handler.consume_batch_id(self.session)
+            second = handler.consume_batch_id(self.session)
+            self.assertEqual(second, first + 1)
+
+            third = handler.consume_batch_id(self.session, as_str=True)
+            self.assertEqual(third, f'{first + 2:08d}')
+
+        def test_should_populate(self):
+            handler = self.make_handler()
+            batch = handler.make_batch(self.session)
+            self.assertFalse(handler.should_populate(batch))
+
+        def test_do_populate(self):
+            handler = self.make_handler()
+            batch = handler.make_batch(self.session)
+            # nb. coverage only; tests nothing
+            handler.do_populate(batch)
+
+        def test_make_row(self):
+            handler = self.make_handler()
+            row = handler.make_row()
+            self.assertIsInstance(row, MockBatchRow)
+
+        def test_add_row(self):
+            handler = self.make_handler()
+            batch = handler.make_batch(self.session)
+            self.session.add(batch)
+            row = handler.make_row()
+            self.assertIsNone(batch.row_count)
+            handler.add_row(batch, row)
+            self.assertEqual(batch.row_count, 1)