No difference reported for required property changed to optional

Openapi-diff does not report a required property that was changed to optional -- removed from the schema "required" array. Changing a required property to optional in an output schema could cause breaking changes if a client relies on a property always being present in a response (because it was marked "required") and the property is then omitted from some responses in the new version.

從命令列工具的 OpenAPI schema 比較開始，追蹤 schema 的 "required" 陣列如何處理。在兩份規格中重現回報的從必要到選用的變化，然後驗證工具會將該變更回報為 breaking。