chore: checkpoint before Python removal

vendor/schemars/tests/struct_additional_properties.rs

@@ -0,0 +1,17 @@
+mod util;
+use schemars::JsonSchema;
+use util::*;
+
+#[allow(dead_code)]
+#[derive(JsonSchema)]
+#[serde(deny_unknown_fields)]
+pub struct Struct {
+    foo: i32,
+    bar: bool,
+    baz: Option<String>,
+}
+
+#[test]
+fn struct_normal_additional_properties() -> TestResult {
+    test_default_generated_schema::<Struct>("struct-normal-additional-properties")
+}