Describe the event source. What app is this for, and what event does the trigger correspond to?
This is a HubSpot trigger that fires when a contact is added to a list. The event corresponds to new list membership additions - specifically
when existing contacts are added to lists or when new contacts are created and immediately added to lists. This trigger ignores contact
property updates and only responds to actual changes in list membership.

Please provide a link to the relevant API docs for the specific service / operation this trigger is tied to.
https://developers.hubspot.com/docs/reference/api/crm/lists#get-%2Fcrm%2Fv3%2Flists%2F%7Blistid%7D%2Fmemberships%2Fjoin-order