Use this method to create an activity that exports contacts and contact
details to a CSV file. By default, all contacts are exported. To filter
contacts to export, specify the source to use, contact_id, list_id,
or segment_id (all mutually exclusive).
By default, all contact related fields are exported. Use the fields
array to only export specific contact fields. You must export email_address
to successfully export email_optin_source, email_optin_date, email_optout_source,
email_optout_date, or email_optout_reason.
After Constant Contact finishes processing the activity, use the results
link in the response body to retrieve the CSV file.