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.

synapse/storage/devices.py

@@ -0,0 +1,77 @@
+# -*- 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.
+import logging
+
+from twisted.internet import defer
+
+from synapse.api.errors import StoreError
+from ._base import SQLBaseStore
+
+logger = logging.getLogger(__name__)
+
+
+class DeviceStore(SQLBaseStore):
+    @defer.inlineCallbacks
+    def store_device(self, user_id, device_id,
+                     initial_device_display_name,
+                     ignore_if_known=True):
+        """Ensure the given device is known; add it to the store if not
+
+        Args:
+            user_id (str): id of user associated with the device
+            device_id (str): id of device
+            initial_device_display_name (str): initial displayname of the
+               device
+            ignore_if_known (bool): ignore integrity errors which mean the
+               device is already known
+        Returns:
+            defer.Deferred
+        Raises:
+            StoreError: if ignore_if_known is False and the device was already
+               known
+        """
+        try:
+            yield self._simple_insert(
+                "devices",
+                values={
+                    "user_id": user_id,
+                    "device_id": device_id,
+                    "display_name": initial_device_display_name
+                },
+                desc="store_device",
+                or_ignore=ignore_if_known,
+            )
+        except Exception as e:
+            logger.error("store_device with device_id=%s failed: %s",
+                         device_id, e)
+            raise StoreError(500, "Problem storing device.")
+
+    def get_device(self, user_id, device_id):
+        """Retrieve a device.
+
+        Args:
+            user_id (str): The ID of the user which owns the device
+            device_id (str): The ID of the device to retrieve
+        Returns:
+            defer.Deferred for a namedtuple containing the device information
+        Raises:
+            StoreError: if the device is not found
+        """
+        return self._simple_select_one(
+            table="devices",
+            keyvalues={"user_id": user_id, "device_id": device_id},
+            retcols=("user_id", "device_id", "display_name"),
+            desc="get_device",
+        )