Tracking Provider API list

Dear @zorem

I used add tracking shipping API.
I can create tracking into order with this input

{
“tracking_provider”:”DHL”,
“tracking_number”: “00340434292070854632”,
“date_shipped”: “2019-11-08”
}

But I got empty tracking provider in response
{
“tracking_id”: “10dda2e3497281dfab2ec769e0d4dc99”,
“tracking_provider”: “”,
“tracking_link”: “”,
“tracking_number”: “00340434292070854632”,
“date_shipped”: “2019-11-08”,

Please provide list of all tracking_provider which I can input in json parameter.

Thanks you