Reads a usage record from a JSON string: the relayed argument of RelayRealtimeUsage. Keeps only the fields a
modality block defines, and only values that are finite numbers of at least 0; a relayed DurationSeconds is
dropped (only a server-side session writes it). null for an absent, blank or malformed string, or one that names
no usage.
Reads a usage record from a JSON string: the relayed argument of
RelayRealtimeUsage. Keeps only the fields a modality block defines, and only values that are finite numbers of at least 0; a relayedDurationSecondsis dropped (only a server-side session writes it).nullfor an absent, blank or malformed string, or one that names no usage.