put https://api.indigitall.com/v2/inapp/audience//contacts/csv
Add contacts from a csv file to an audience. Only can add externalId. For removing users from an audience, there is other endpoint. All the previous externals Id will be removed.
CSV format example: ~ externalId be5d3f02-f486-47e2-bd98-5128e1c4b065 ~