feat: add basic support for wutta-continuum

and i mean *basic* - so far..  eventually will expose version history
for viewing etc.

unfortunately got carried away and reorganized the api docs a little
while i was at it..

tests/db/test_continuum.py

@@ -0,0 +1,38 @@
+# -*- coding: utf-8; -*-
+
+from unittest.mock import patch, MagicMock
+
+import pytest
+
+from tests.util import WebTestCase
+
+from wuttaweb.db import continuum as mod
+
+
+class TestWuttaWebContinuumPlugin(WebTestCase):
+
+    def setUp(self):
+        if not hasattr(mod, 'WuttaWebContinuumPlugin'):
+            pytest.skip("test not relevant without sqlalchemy-continuum")
+        self.setup_web()
+
+    def make_plugin(self):
+        return mod.WuttaWebContinuumPlugin()
+
+    def test_get_remote_addr(self):
+        plugin = self.make_plugin()
+
+        with patch.object(mod, 'get_current_request', return_value=None):
+            self.assertIsNone(plugin.get_remote_addr(None, self.session))
+
+        self.request.client_addr = '127.0.0.1'
+        self.assertEqual(plugin.get_remote_addr(None, self.session), '127.0.0.1')
+
+    def test_get_user_id(self):
+        plugin = self.make_plugin()
+
+        with patch.object(mod, 'get_current_request', return_value=None):
+            self.assertIsNone(plugin.get_user_id(None, self.session))
+
+        self.request.user = MagicMock(uuid='some-random-uuid')
+        self.assertEqual(plugin.get_user_id(None, self.session), 'some-random-uuid')