[tor-relays] Opening metrics-api.torproject.org for testing

[Hiro]

Hello everyone,

As part of our redesign of the metrics pipeline, we have developed a new 
API that will eventually replace Onionoo: the Network Status API (aka NSA).

We are now opening NSA for testing, and it can be accessed at: 
https://metrics-api.torproject.org.

Documentation is available here: 
https://gitlab.torproject.org/tpo/network-health/metrics/networkstatusapi/-/tree/main/docs.

Please note that the API may be unstable at times, and some results 
might be inconsistent. Onionoo will remain our primary data source for 
relay search at least until the end of the year.

We welcome any suggestions or feedback regarding the types of 
information that should be included in the API. You can provide feedback 
by opening an issue on the repository or by replying to this email.

Thank you.

-hiro