Add Visitor trait, update changelog

schemars/tests/docs.rs

@@ -58,7 +58,7 @@ fn doc_comments_struct() -> TestResult {
 
 #[test]
 fn doc_comments_struct_ref_siblings() -> TestResult {
-    let settings = SchemaSettings::draft07().with(|s| s.allow_ref_siblings = true);
+    let settings = SchemaSettings::draft2019_09();
     test_generated_schema::<MyStruct>("doc_comments_struct_ref_siblings", settings)
 }
 

schemars/tests/expected/doc_comments_struct_ref_siblings.json

@@ -1,5 +1,5 @@
 {
-  "$schema": "http://json-schema.org/draft-07/schema#",
+  "$schema": "https://json-schema.org/draft/2019-09/schema",
   "title": "This is the struct's title",
   "description": "This is the struct's description.",
   "type": "object",