We create a custom histogram metric that logs the userID
when the observed value is greater or equal to the last bucket value.
This allows us to start tracking the slowest users of a system
while at the same time not polluting the Prometheus metrics
by storing a userID for every observation.
https://mattermost.atlassian.net/browse/MM-61887
```release-note
NONE
```
a6d37fa14c