Generates a new public URL for a contact with provided email to manage their mailing list subscriptions.
Bearer authentication header of the form Bearer <token>, where <token> is your auth token.
The email of a contact in your project's contact list, who to create the portal session for.
URL to redirect the user to when they tap on that they're cone editing their lists, or when the session is expired.
"https://example.com/projects/123456/notification_settings"