Healthcheck page description needs updating

[radyakin]

The healthcheck page describes the health status only in relation to export service functioning:

Overall server health check
The following can be the statuses for the healthcheck:

Healthy (green) - export service is responding and can access headquarters;
Degraded (yellow) - export service is not answering;
Unhealthy (red) - export service cannot access headquarters;

Checks for other factors were subsequently added that can also affect the overall health status. Their effect needs to be described in the article.