Add support for Casdoor authentication

[MayankMittal1]

Using Casdoor for auth over in-house authentication method.
Features:

1. Front-end and back-end separate architecture, developed by Golang, Casdoor supports high concurrency, provides web-based managing UI and supports multiple languages(Chinese, English).
2. Casdoor supports Github, Google, QQ, WeChat third-party applications login, and support the extension of third-party login with plugins.
3. With Casbin based authorization management, Casdoor supports ACL, RBAC, ABAC, RESTful accessing control models.
4. Phone verification code, email verification code and forget password features.
5. Accessing logs auditing and recording.
6. Casdoor supports integration with existing systems using db sync method, users can transition to Casdoor smoothly.
7. Casdoor supports mainstream databases: MySQL, PostgreSQL, SQL Server etc, and support the extension of new database with plugins.