## About the changes
Some of our metrics are not labeled correctly, one example is
`<base-path>/api/frontend/client/metrics` is labeled as
`/client/metrics`. We can see that in internal-backstage/prometheus:
This issue affects all endpoints that fail to validate the request body.
Also, endpoints that are rejected by the authorization-middleware or the
api-token-middleware are reported as `(hidden)`.
To gain more insights on our api usage but being protective of metrics
cardinality we're prefixing `(hidden)` with some well known base urls:
https://github.com/Unleash/unleash/pull/6400/files#diff-1ed998ca46ffc97c9c0d5d400bfd982dbffdb3004b78a230a8a38e7644eee9b6R17-R33
## How to reproduce:
Make an invalid call to metrics (e.g. stop set to null), then check
/internal-backstage/prometheus and find the 400 error. Expected to be at
`path="/api/client/metrics"` but will have `path=""`:
```shell
curl -H"Authorization: *:development.unleash-insecure-client-api-token" -H'Content-type: application/json' localhost:4242/api/client/metrics -d '{
"appName": "bash-test",
"instanceId": "application-name-dacb1234",
"environment": "development",
"bucket": {
"start": "2023-07-27T11:23:44Z",
"stop": null,
"toggles": {
"myCoolToggle": {
"yes": 25,
"no": 42,
"variants": {
"blue": 6,
"green": 15,
"red": 46
}
},
"myOtherToggle": {
"yes": 0,
"no": 100
}
}
}
}'
```
