Accessing response headers in API routes of App Router?

[art-alexeyenko]

Summary

API route handlers in Pages Router had access to both Request and Response objects, so you could read response headers like Set-Cookie, Access-Control-Allow-Origin and others.
App Router's GET, POST and other handler functions only accept a Request object.
Now, NextRequest type allows to access Set-Cookie. But what about other headers, like CORS set by next.config rules?

Additional information

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Example

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