get https://aptos-mainnet.nodereal.io/v1/{api_key}/v1/-/healthy
By default this endpoint just checks that it can get the latest ledger
info and then returns 200.
If the duration_secs param is provided, this endpoint will return a
200 if the following condition is true:
server_latest_ledger_info_timestamp >= server_current_time_timestamp - duration_secs