function assignSyntheticsInfoHeader(header, encKey, transaction) {
  const synthInfoData = parseSyntheticsInfoHeader(header, encKey)
  if (!synthInfoData) {
    return
  }

  transaction.syntheticsInfoData = synthInfoData
  transaction.syntheticsInfoHeader = header
}
Take the X-NewRelic-Synthetics-Info header and apply any appropriate data to the
transaction for later use. This is the gate keeper for attributes being
added onto the transaction object for synthetics info.

@param {string} header - The raw X-NewRelic-Synthetics-Info header
@param {string} encKey - Encoding key handed down from the server
@param {object} transaction - Where the synthetics data is attached to.