next.js

c0e8e55a - Add test for external middleware rewrite with changed headers (#49606)

Add test for external middleware rewrite with changed headers (#49606) ### What? Within Issue https://github.com/vercel/next.js/issues/48040 / PR #49487 the middleware proxy for external rewrites was fixed. Unfortunately, this does not work when you change the headers in your middleware (according to https://vercel.com/templates/next.js/edge-functions-modify-request-header) ### Why? We still have issues with the latest canary ### How? Unfortunately I was not able to find the issue, just recreating the bug in a testcase --------- Co-authored-by: Tim Neutkens <tim@timneutkens.nl>