Shohei MaedaandGitHub 3f164abd25 Add cache-control header on 304 response (#50408) ...

Next.js currently does not return `cache-control` header on 304 response. Accordingly to RFC, Next.js should include it as well: https://www.rfc-editor.org/rfc/rfc9110#section-15.4.5

> The server generating a 304 response MUST generate any of the following header fields that would have been sent in a [200 (OK)](https://www.rfc-editor.org/rfc/rfc9110#status.200) response to the same request:
> 
> - [Content-Location](https://www.rfc-editor.org/rfc/rfc9110#field.content-location), [Date](https://www.rfc-editor.org/rfc/rfc9110#field.date), [ETag](https://www.rfc-editor.org/rfc/rfc9110#field.etag), and [Vary](https://www.rfc-editor.org/rfc/rfc9110#field.vary)
> - **_Cache-Control_** and Expires (see [[CACHING](https://www.rfc-editor.org/rfc/rfc9110#CACHING)])

2023-05-28 12:44:11 +00:00

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