Add prompt

Author: lixiachena

src/azure-cli/azure/cli/command_modules/sql/custom.py

@@ -3140,6 +3140,12 @@ def update_long_term_retention(
         if time_based_immutability_mode.lower() not in ['unlocked', 'locked']:
             raise CLIError('Invalid value for time-based immutability mode. '
                            'Valid values are "unlocked" or "locked".')
+        if time_based_immutability_mode.lower() == 'locked':
+            if not yes:
+                confirmation = prompt_y_n("""Once locked, immutable backups cannot be modified or deleted for the full retention period. There is no extra cost to enable immutability, but standard backup storage charges apply. Note: The logical Azure SQL Server cannot be deleted during the retention period.
+            Do you want to proceed?""")
+                if not confirmation:
+                    return
 
     kwargs['weekly_retention'] = weekly_retention