Spring Security OAuth 2 Tutorial - 1 : Getting familiar with OAuth 2 concepts

First part of a 10-part tutorial series on implementing OAuth 2.0 security with Spring Security and Keycloak. Covers core OAuth 2.0 concepts including the four roles (Resource Owner, Resource Server, Client, Authorization Server), the five grant types, and the distinction between OAuth 2.0 (authorization) and OpenID Connect (authentication). Includes a practical walkthrough of setting up Keycloak via Docker Compose, creating a realm, configuring a client with proper authentication settings, and creating a test user.