Context:
See parent task.

AT:

• while the alert webhook currently only supports one placeholder key that allows to inject the whole alert message (ALERT_MESSAGE) the following atomic parts should also have dedicated placeholders that can be used to compose alert webhook payloads:
  ALERT_NAME, sample value "Some Alert"
  ALERT_REPORT_LINK, sample value "http://https://stage.optimize.camunda.cloud/#/report/b4a8ec72-55b1-46a2-b944-c9bd314e0b7b/"
  ALERT_CURRENT_VALUE, sample value "400"
  ALERT_THRESHOLD_VALUE, sample value "100"
  ALERT_THRESHOLD_OPERATOR, sample value "<" OR ">"
  ALERT_TYPE, with the values values "new", "reminder", "resolved" indicating whether this alert is freshly triggered, a reminder or actually resolved
  ALERT_INTERVAL, sample value "5"
  ALERT_INTERVAL_UNIT, sample value "minutes"

Out of scope:
docs will be done separately