apache-airflow-providers-keycloak: Missing OAuth 2.0 State and PKCE Enables Login CSRF and Session Fixation

The Keycloak authentication manager in `apache-airflow-providers-keycloak` did not generate or validate the OAuth 2.0 `state` parameter on the login / login-callback flow, and did not use PKCE. An attacker with a Keycloak account in the same realm could deliver a crafted callback URL to a victim's browser and cause the victim to be logged into the attacker's Airflow session (login-CSRF / session fixation), where any credentials the victim subsequently stored in Airflow Connections would be harvestable by the attacker. Users are advised to upgrade `apache-airflow-providers-keycloak` to 0.7.0 or later.