additionalProperties: false for struct annotated with serde deny_unknown_fields (#30)

Co-authored-by: Denis Kurilov <denis@routinghub.com>

schemars/tests/expected/struct-normal-additional-properties.json

@@ -0,0 +1,25 @@
+{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "title": "Struct",
+  "type": "object",
+  "additionalProperties": false,
+  "required": [
+    "bar",
+    "foo"
+  ],
+  "properties": {
+    "bar": {
+      "type": "boolean"
+    },
+    "baz": {
+      "type": [
+        "string",
+        "null"
+      ]
+    },
+    "foo": {
+      "type": "integer",
+      "format": "int32"
+    }
+  }
+}

schemars/tests/struct_additional_properties.rs

@@ -0,0 +1,16 @@
+mod util;
+use schemars::JsonSchema;
+use util::*;
+
+#[derive(Debug, 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")
+}