Implement metrics and measurements to track API performance

### User story

Before we start improving our APIs, we should implement metrics and measurements.

Performance of the API should be improved drastically, as proven by benchmarks.
We need metrics for endpoint performance times so we can see if some changes are making APIs slower or faster.
Track time from request coming in to response coming out.

Please also research whether we want to use or already have tooling to measure API performance or if we need to build something specifically for our needs.

### Acceptance criteria

- it should be possible to cover different API endpoints without a lot of effort (store API / admin API)
- invocation times are available for reviewing (API monitoring)