Create a custom export based on the given template_id. To find a template_id, use List Export Templates.
The 'file_url' will expire 1 week from creation - this is to ensure your exports are up to date!
NOTE: id vs. template_id
The 'id' refers to the id of this export, whereas the 'template_id' refers to the source template. You'll use the make sure to use 'id' to GET the export that you've created.