Account for ASP.NET Core changes around proxy header handling

[TimHess]

Description

Provides a fix for #1524 that is automatically implemented for certificate auth

Quality checklist

• [ ] Your code complies with our Coding Style.
• [ ] You've updated unit and/or integration tests for your change, where applicable.
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[TimHess]

Thanks for diving into this. I haven't tested the changes, assuming you did.

Yes, but also because https://github.com/SteeltoeOSS/Samples/pull/391 works with the same set of sample apps and I was hitting weird probably-environment issues during my first round of testing, I was already planning to leave this PR draft/open while wrapping up the other effort

[sonarqubecloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

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