Reason-phrase reproduction
==========================

ASP.NET Core / Kestrel sets a custom HTTP/1.1 reason phrase on the status
line. We need that phrase to survive to the client.

  GET /reason-phrase          -> sends: HTTP/1.1 401 ActivationNotFound
  GET /reason-phrase/{phrase} -> sends: HTTP/1.1 401 {phrase}
  GET /ok-phrase              -> sends: HTTP/1.1 200 EverythingIsFine
  GET /echo                   -> what the container sees
  GET /health                 -> ok

Compare the first line of the response:

  curl -i -s https://<this-service>/reason-phrase | head -1

Expected (and what the container sends):
  HTTP/1.1 401 ActivationNotFound

Observed through the platform router:
  HTTP/1.1 401 Unauthorized

Why it matters: a desktop application in the field reads
HttpWebResponse.StatusDescription to decide which error occurred. Those
clients are installed on customer machines and cannot be updated, so the
phrase is a fixed part of the contract.