Add Feishu Oauth client

[CHEN-Jing194]

Hello,

Thank you very much for your outstanding project. I have successfully implemented the Feishu OAuth2 process using your project. Would it be possible for me to contribute the Feishu OAuth client I developed to your project? Feishu (also known as Lark outside of China) is a popular team collaboration platform in China, and I believe this would be beneficial to many Chinese developers. Once again, thank you for your exceptional work.

Best regards,

[frankie567]

Why not! We already have some local services implemented, so yes, open to review a PR with it!