Cape server. No web UI. No setup, No bullshit.
Originally meant for Serene Minecraft Client, some legacy code such as cape prices was left in but commented out.
Deploy to a PHP-enabled web server, create a key and add some users.
The auth-flow file contains some original auth keys. I suggest making your own, they can be any string. When sending requests, you'll need to encrypt the string with the password left in the same file.
You still need a mod to display these. I'll be releasing one soon.