fix: Clear registry before updating it with new values to clear remov…

[dploeger]

…ed credentials

Fixes #11

[mkoertgen]

Thanks for the contribution @dploeger.

A small question for my understanding: When clearing the expired metrics on any observe we will probably lose track of old apps. I guess this is no problem when we rely on prometheus scraping the endpoint frequently enough, right?

[dploeger]

A small question for my understanding: When clearing the expired metrics on any observe we will probably lose track of old apps. I guess this is no problem when we rely on prometheus scraping the endpoint frequently enough, right?

Yes, exactly. In my view, exporters are only responsible to return the current state of things. Prometheus is responsible for storing history.