httpauth is not attached to replay request

[ryanisn]

Problem Description

I set mitmproxy to run in reverse mode as a proxy to real server, and then protect mitmproxy with a pair of user:pass in the proxyauth option. A regular request would go through, but a reply of that same request would return 401 Unauthorized

Steps to reproduce the behavior:

1. turn on reverse mode in mitmweb
2. set basic auth in proxyauth in 'username:pass' format
3. initiate a success request
4. replay the request

System Information

Mitmproxy: 10.1.5
Python: 3.11.6
OpenSSL: OpenSSL 3.1.4 24 Oct 2023
Platform: Linux-4.14.276-211.499.amzn2.x86_64-x86_64-with-glibc2.31