fix #18, cache users from fediverse

server/api/models/fed_users.js

@@ -0,0 +1,13 @@
+module.exports = (sequelize, DataTypes) => {
+  const fed_users = sequelize.define('fed_users', {
+    ap_id: {
+      type: DataTypes.STRING,
+      primaryKey: true
+    },
+    object: DataTypes.JSON
+  }, {})
+  fed_users.associate = function(models) {
+    // associations can be defined here
+  };
+  return fed_users
+}