feat: add basic "create order" feature, docs, tests

just the package API docs so far, narrative will come later

tests/db/model/test_customers.py

@@ -0,0 +1,15 @@
+# -*- coding: utf-8; -*-
+
+from wuttjamaican.testing import DataTestCase
+
+from sideshow.db.model import customers as mod
+
+
+class TestPendingCustomer(DataTestCase):
+
+    def test_str(self):
+        customer = mod.PendingCustomer()
+        self.assertEqual(str(customer), "")
+
+        customer.full_name = "Fred Flintstone"
+        self.assertEqual(str(customer), "Fred Flintstone")