(Optional) The transaction name that this alert monitors.
The transaction response time percentile to use for alerting.
If the {{phraseForValue()}} over the given time period exceeds this threshold, then alert will be
triggered.
Alert if the {{phraseForValue()}} drops below the threshold, instead of alerting if the
{{phraseForValue()}} exceeds the threshold.
The time period over which the {{phraseForValue()}} is calculated.
Time periods with very few transactions have much less meaningful metrics, so this can be used to
suppress alerts from being generated unless the time period has a minimum transaction count.