New tests only. MetricsAuth on its own answers 401 with a challenge
without credentials or with a wrong username or password, and lets the
configured ones through. A CORS preflight request gets the same
Access-Control-Allow-Origin as a GET. A POST / carrying the signing key
leaves the key out of the request log line, and the login handler's own
log lines leave out the submitted key. The metrics middleware on its own
records a request it served; the router records nothing while no metrics
username is set.
Not tested through the router: the basic auth in front of /metrics and
recording with a metrics username set (#180).
The pinned basicauth-go compares the password in constant time.
Model: opus-5-5
