Add device_id support to /login

Add a 'devices' table to the storage, as well as a 'device_id' column to
refresh_tokens.

Allow the client to pass a device_id, and initial_device_display_name, to
/login. If login is successful, then register the device in the devices table
if it wasn't known already. If no device_id was supplied, make one up.

Associate the device_id with the access token and refresh token, so that we can
get at it again later. Ensure that the device_id is copied from the refresh
token to the access_token when the token is refreshed.

tests/handlers/test_device.py

@@ -0,0 +1,75 @@
+# -*- coding: utf-8 -*-
+# Copyright 2016 OpenMarket Ltd
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from twisted.internet import defer
+
+from synapse.handlers.device import DeviceHandler
+from tests import unittest
+from tests.utils import setup_test_homeserver
+
+
+class DeviceHandlers(object):
+    def __init__(self, hs):
+        self.device_handler = DeviceHandler(hs)
+
+
+class DeviceTestCase(unittest.TestCase):
+    @defer.inlineCallbacks
+    def setUp(self):
+        self.hs = yield setup_test_homeserver(handlers=None)
+        self.hs.handlers = handlers = DeviceHandlers(self.hs)
+        self.handler = handlers.device_handler
+
+    @defer.inlineCallbacks
+    def test_device_is_created_if_doesnt_exist(self):
+        res = yield self.handler.check_device_registered(
+            user_id="boris",
+            device_id="fco",
+            initial_device_display_name="display name"
+        )
+        self.assertEqual(res, "fco")
+
+        dev = yield self.handler.store.get_device("boris", "fco")
+        self.assertEqual(dev["display_name"], "display name")
+
+    @defer.inlineCallbacks
+    def test_device_is_preserved_if_exists(self):
+        res1 = yield self.handler.check_device_registered(
+            user_id="boris",
+            device_id="fco",
+            initial_device_display_name="display name"
+        )
+        self.assertEqual(res1, "fco")
+
+        res2 = yield self.handler.check_device_registered(
+            user_id="boris",
+            device_id="fco",
+            initial_device_display_name="new display name"
+        )
+        self.assertEqual(res2, "fco")
+
+        dev = yield self.handler.store.get_device("boris", "fco")
+        self.assertEqual(dev["display_name"], "display name")
+
+    @defer.inlineCallbacks
+    def test_device_id_is_made_up_if_unspecified(self):
+        device_id = yield self.handler.check_device_registered(
+            user_id="theresa",
+            device_id=None,
+            initial_device_display_name="display"
+        )
+
+        dev = yield self.handler.store.get_device("theresa", device_id)
+        self.assertEqual(dev["display_name"], "display")