如何在Flask-JWT中设置自定义授权响应？

from flask import Flask, jsonify
from flask_jwt import JWT, jwt_required, current_identity
from werkzeug.security import safe_str_cmp

app = Flask(__name__)
app.config['SECRET_KEY'] = 'secret-key'

# 用户模型
class User(object):
    def __init__(self, id, username, password):
        self.id = id
        self.username = username
        self.password = password

# 用户认证回调函数
def authenticate(username, password):
    users = [
        User(1, 'user1', 'password1'),
        User(2, 'user2', 'password2')
    ]
    for user in users:
        if user.username == username and safe_str_cmp(user.password.encode('utf-8'), password.encode('utf-8')):
            return user

# 身份认证回调函数
def identity(payload):
    user_id = payload['identity']
    users = [
        User(1, 'user1', 'password1'),
        User(2, 'user2', 'password2')
    ]
    for user in users:
        if user.id == user_id:
            return user

# 自定义未授权访问响应
@jwt.unauthorized_loader
def unauthorized_callback(error):
    return jsonify({'message': 'Unauthorized access', 'error': 'authentication_required'}), 401

# JWT配置
jwt = JWT(app, authenticate, identity)

# 受保护的路由
@app.route('/protected')
@jwt_required()
def protected():
    return jsonify({'message': 'Protected endpoint', 'user_id': current_identity.id})

if __name__ == '__main__':
    app.run()