Get access to OS X Server user database

Hello,

I would like to get access to OS X Server user database: I'm creating an HTML page, where users should change their passwords or account names. It would being better if the whole actions are automatic, so for example there's a form, where the user fills in his username and password. Then he can choose from an option (change user name, change password, ...). I know, there's an official website for changing password, but it's another design and has too less options.

How do I realize the login?