ensure_correct_media_type does not set response Content-Type to application/vnd.api+json

I noticed that when the ensure_correct_media_type before_action is run, and validation fails (Content-Type is not application/vnd.api+json, that the response from the server has a Content-Type header set to application/json. According to the spec, shouldn't this failed validation also return a Content-Type header of application/vnd.api+json?

Thanks ahead of time for the help.

定位 ensure_correct_media_type before_action，并跟踪由于 Content-Type 不是 application/vnd.api+json 而导致验证失败时构建的响应。检查现有的响应处理和测试（如果有）。当验证失败时返回带有 JSON:API 规范所要求的 application/vnd.api+json Content-Type 的响应，即表示完成。