REDHAT-BUG-2527140: High severity Ansible automation-controller vulnerability

A flaw was found in automation-controller (AWX). Four compounding issues let a holder of object-level NotificationTemplate admin recover the plaintext of notification credentials for fixed-endpoint backends: (1) NotificationTemplate.displaynotificationconfiguration() (awx/main/models/ notifications.py) masks only password subfields of the CURRENT notification type, so after a type change the previous type's password subfield is returned with its full Fernet ciphertext; (2) NotificationTemplateSerializer.validate() (awx/api/ serializers.py) returns early when notificationconfiguration is absent from the request body, allowing a type-only change that keeps the stale ciphertext; (3) NotificationTemplate.save() skips re-encryption of any value beginning with "$encrypted$" and the serializer's forward sentinel tests exact equality with "$encrypted$", so a full ciphertext replanted into a different password subfield is stored verbatim; (4) getencryptionkey() (awx/main/utils/encryption.py) derives the Fernet key from the secret key, primary key, and field name only -- not the subfield -- so a ciphertext produced for one subfield decrypts as any other subfield of the same object. Chaining these, an attacker switches the template type to leak the ciphertext, replants it into a webhook password with an attacker-controlled URL, and triggers /test/; the controller decrypts and sends the plaintext to the attacker in an HTTP Basic auth header. Verified live on AAP 2.7 / automation-controller 4.8.1; still present on devel. Upstream: github.com/ansible/awx (awx/main/models/notifications.py; awx/api/serializers.py; awx/main/utils/encryption.py; awx/main/notifications/webhookbackend.py)