add ca download route

migrations/015-paired_devices.js

@@ -0,0 +1,17 @@
+var db = require('./db')
+
+exports.up = function (next) {
+  var sql = [
+    'alter table devices drop authorized',
+    'alter table devices drop unpair',
+    `create table paired_devices (
+      device_id text PRIMARY KEY,
+      created timestamptz NOT NULL default now()
+    )`
+  ]
+  db.multi(sql, next)
+}
+
+exports.down = function (next) {
+  next()
+}