fix: add _aes attribute to Fernet256 for cryptography>=50.0.0 compatibility (#16654)

Cryptography 50.0.0 added a self._aes attribute to the Fernet class
constructor. Since Fernet256 overrides __init__ without calling
super().__init__(), it needs to manually set this attribute.

Without this attribute, any code using Fernet256 (encryption/decryption
of credentials, secrets, etc.) fails with:
    AttributeError: 'Fernet256' object has no attribute '_aes'

This fix:
- Imports algorithms from cryptography.hazmat.primitives.ciphers
- Sets self._aes = algorithms.AES(self._encryption_key) in __init__

The fix is backward compatible with cryptography < 50.0.0 since the
_aes attribute wasn't used by Fernet's methods in older versions.

Fixes: 277 test failures in AWX test suite when using cryptography 50.x
Related: pyca/cryptography#11234 (cryptography 50.0.0 changes)

Co-authored-by: Stevenson Michel <iamstevensonmichel@outlook.com>

awx/main/utils/encryption.py

@@ -7,6 +7,7 @@ from collections import namedtuple
 
 from cryptography.fernet import Fernet, InvalidToken
 from cryptography.hazmat.backends import default_backend
+from cryptography.hazmat.primitives.ciphers import algorithms
 from django.utils.encoding import smart_str, smart_bytes
 
 __all__ = ['get_encryption_key', 'encrypt_field', 'decrypt_field', 'encrypt_value', 'decrypt_value', 'encrypt_dict']
@@ -30,6 +31,8 @@ class Fernet256(Fernet):
         self._signing_key = key[:32]
         self._encryption_key = key[32:]
         self._backend = backend
+        # Required for compatibility with cryptography >= 50.0.0
+        self._aes = algorithms.AES(self._encryption_key)
 
 
 def get_encryption_key(field_name, pk=None, secret_key=None):