Use pure IETF Health Check standard

[manuio]

ENHANCEMENT

1. Describe the enhancement you are requesting. Enhancements include:
   Currently we support the IETF Health Check standard but with 2 extra custom fields build_time and commit:

{"status":"pass","version":"0.12.1","commit":"d3c3638f54fbf56b2c2bb23804813746358e5ca7","description":"things service","build_time":"2022-01-20_11:22:22"}

These fields are not standard and we have to decide if we want to use description field to put this information or if we combine standard and custom fields.

2. Indicate the importance of this enhancement to you (must-have, should-have, nice-to-have).
   nice-to-have

[drasko]

Depends on inadarei/rfc-healthcheck#76