AG5-2: Implement authentication logic with support for multiple authen protocol

[akraradets]

Issue

AITGPT needs to have authentication.
What we believe is that integrating with AITSIS will be done via LDAP.
However, we also want AITGPT to be able to integrate via other standard authentication protocols.

To do

• Implement authentication logic with user model (id, name, group/role)
• Binding authentication with LDAP
• Binding authentication with other service (will discuss later)