public function update(User $administrator, Request $request)
    {
        $this->validate($request, [
            'firstname' => 'required',
            'lastname'  => 'required',
            'roles'     => 'required|array',
        ]);

        $this->updateEntry($administrator, $request->only([
            'firstname',
            'lastname',
            'cellphone',
            'telephone',
            'born_at'
        ]));

        $administrator->roles()->sync(input('roles'));

        return redirect_to_resource();
    }