?campaign_id={campaign_id} to the URL to allow the customer to
unsubscribe from a specific campaign. Otherwise it defaults to all current
campaignsBasic authentication header of the form Basic <encoded-value>, where <encoded-value> is the base64-encoded string username:password.
The ID of the unsubscribe embed
The embeddable HTML that will render a UI for unsubscribing from a campaign
The response is of type string.