Fix broken signup/login for students

The current backend process of login for student is:

• Create user
• If role == 'mahasiswa', fetch student detail and create Student object

This process is broken because fetching student's detail from https://api.cs.ui.ac.id/siakngcs/mahasiswa/{npm}/ requires authentication which is not currently provided, the front end will always show that username/password is wrong even though it is correct because of the 403 error.

This fix will instead create student's object based on simple information from https://api.cs.ui.ac.id/authentication/ldap/v2/ response and let student's edit information such as birth place, birth date, major, and batch after they are successfully logged in.