getUrl method
Replace the variables in url with the specified runtime values, if the variables are present.
Implementation
String getUrl(
        String participantId, String studyDeploymentId, int triggerId) =>
    url
        .replaceFirst('\$PARTICIPANT_ID', participantId)
        .replaceFirst('\$DEPLOYMENT_ID', studyDeploymentId)
        .replaceFirst('\$TRIGGER_ID', triggerId.toString());