[Core] az extension add/update and az upgrade: Pre-announcement default value change from true to false for --allow-preview (#30162)

* preannounce change of allow-preview default value

Author: AllyW

src/azure-cli/azure/cli/command_modules/extension/_breaking_change.py

@@ -0,0 +1,12 @@
+# --------------------------------------------------------------------------------------------
+# Copyright (c) Microsoft Corporation. All rights reserved.
+# Licensed under the MIT License. See License.txt in the project root for license information.
+# --------------------------------------------------------------------------------------------
+
+from azure.cli.core.breaking_change import register_default_value_breaking_change
+
+register_default_value_breaking_change('extension add', '--allow-preview',
+                                       'true', 'false')
+register_default_value_breaking_change('extension update', '--allow-preview',
+                                       'true', 'false')
+# The default value of '--allow-preview' will be changed to 'false' from 'true' in next breaking change release(2.67.0).

src/azure-cli/azure/cli/command_modules/util/_breaking_change.py

@@ -0,0 +1,10 @@
+# --------------------------------------------------------------------------------------------
+# Copyright (c) Microsoft Corporation. All rights reserved.
+# Licensed under the MIT License. See License.txt in the project root for license information.
+# --------------------------------------------------------------------------------------------
+
+from azure.cli.core.breaking_change import register_default_value_breaking_change
+
+register_default_value_breaking_change('upgrade', '--allow-preview',
+                                       'true', 'false')
+# The default value of '--allow-preview' will be changed to 'false' from 'true' in next breaking change release(2.67.0).