Migrate clientapi storage to use migrate library

db-schema/devices/1511791787_initial.down.sql

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+DROP TABLE IF EXISTS device_devices;

db-schema/devices/1511791787_initial.up.sql

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+-- Stores data about devices.
+CREATE TABLE IF NOT EXISTS device_devices (
+    -- The access token granted to this device. This has to be the primary key
+    -- so we can distinguish which device is making a given request.
+    access_token TEXT NOT NULL PRIMARY KEY,
+    -- The device identifier. This only needs to uniquely identify a device for a given user, not globally.
+    -- access_tokens will be clobbered based on the device ID for a user.
+    device_id TEXT NOT NULL,
+    -- The Matrix user ID localpart for this device. This is preferable to storing the full user_id
+    -- as it is smaller, makes it clearer that we only manage devices for our own users, and may make
+    -- migration to different domain names easier.
+    localpart TEXT NOT NULL,
+    -- When this devices was first recognised on the network, as a unix timestamp (ms resolution).
+    created_ts BIGINT NOT NULL,
+    -- The display name, human friendlier than device_id and updatable
+    display_name TEXT
+    -- TODO: device keys, device display names, last used ts and IP address?, token restrictions (if 3rd-party OAuth app)
+);
+
+-- Device IDs must be unique for a given user.
+CREATE UNIQUE INDEX IF NOT EXISTS device_localpart_id_idx ON device_devices(localpart, device_id);