v1.1.0: Add getUserInfo method to retrieve user information from Keycloak

- Implemented getUserInfo method in KeycloakBearerUserProvider to fetch user details from the Keycloak userinfo endpoint using access token.
- The method sends a GET request to the Keycloak userinfo endpoint with the Bearer token for authorization.
- Handles error responses from Keycloak and throws a CustomUserMessageAuthenticationException if user info retrieval fails.