Create markers from file
POST
{{cartes_api_base_url}}/maps/{{cartes_map_uuid}}/markers/file
curl -X POST 'cartes_api_base_url/maps/048eebe4-8dac-46e2-a947-50b6b8062fec/markers/file' -H 'Accept: application/json' -H 'Content-Type: application/json' -F '{"name"=>"file=@\"/Users/mwargan/Downloads/ashland.gpx\";", "value"=>"", "datatype"=>"null"}=' -F '{"name"=>"file", "value"=>nil, "datatype"=>"null"}='