feat: add confirmation to migrate command

it operates on a potentially large number of groups, so this adds a
layer of protection against mistakes

littlepay/main.py

@@ -64,7 +64,12 @@ def _maincmd(name, help):
     groups_link = _subcmd(groups_commands, "link", help="Link one or more concession groups to a product")
     groups_link.add_argument("product_id", help="The ID of the product to link to")
 
-    _subcmd(groups_commands, "migrate", help="Migrate a group from the old Customer Group format to the current format")
+    groups_migrate = _subcmd(
+        groups_commands, "migrate", help="Migrate a group from the old Customer Group format to the current format"
+    )
+    groups_migrate.add_argument(
+        "--force", action="store_true", default=False, help="Don't ask for confirmation before migration"
+    )
 
     groups_products = _subcmd(groups_commands, "products", help="List products for one or more concession groups")
     groups_products.add_argument(

tests/test_main.py

@@ -140,6 +140,16 @@ def test_main_groups_migrate(mock_commands_groups):
     assert call_args.group_command == "migrate"
 
 
+def test_main_groups_migrate_force(mock_commands_groups):
+    result = main(argv=["groups", "migrate", "--force"])
+
+    assert result == RESULT_SUCCESS
+    mock_commands_groups.assert_called_once()
+    call_args = mock_commands_groups.call_args.args[0]
+    assert call_args.group_command == "migrate"
+    assert call_args.force is True
+
+
 def test_main_groups_products(mock_commands_groups):
     result = main(argv=["groups", "products"])