Add Doc for Agent Identity

[kalaiyarasiganeshalingam]

Purpose

$Subject

Summary by CodeRabbit

• Documentation

  • Added a new Identity & Access Management guide for securing AI agents and configuring authentication/authorization.
  • Enhanced Creating an Agent guide with clearer chat and inline agent wizard guidance, UI screenshots, expanded configuration tables, and a full example.
  • Clarified agent overview and updated "What’s next" links across agent docs to include Identity & Access Management.

• Chores

  • Updated documentation sidebar ordering and added the new Identity & Access Management entry; adjusted Observability page position.