schemaId property
Gets the unique identifier for this OpenMHealth schema.
The schema ID typically follows the format "omh:schema-name:version.number" (e.g., "omh:heart-rate:2.0" or "omh:body-temperature:4.0").
@return The schema identifier string.
Implementation
@override
String get schemaId => "omh:heart-rate-variability:1.0";