The new test sends two paths one route answers and three requests no
route answers through the metrics middleware, and expects the handler
label to hold the route's pattern and "unmatched". It fails: the label
is each request's path, so every new path adds series.
TestMetricsRecordsServedRequest serves its request outside any router,
so it now expects handler="unmatched" where it expected the path
handler="/test", as the owner approved in
#254 (comment).
Middleware gets a metricsRegistry field, nil being Prometheus' default
registry, so the new test can register with a registry of its own:
TestMetricsRecordsServedRequest registers with the default one.
Model: opus-5-5
sneak
c49c7a3c3e