Updated role model and created perm model in API

api/models/permission-model.js

@@ -0,0 +1,13 @@
+const bookshelf = require('../database/bookshelf').bookshelf
+
+require('./role-model')
+
+let Permission = bookshelf.Model.extend({
+    tableName: 'permission',
+    hidden: [ 'id' ],
+    role() {
+        return this.belongsToMany( 'Role', 'role_permission' )
+    }
+})
+
+module.exports = bookshelf.model( 'Permission', Permission );