Issues a JWT Bearer Token using application credentials (client_credentials grant).

Required Content-Type: application/x-www-form-urlencoded

Developer flow:

1. Send the client_id and client_secret provided by AnkaTech
2. Copy the access_token from the response
3. Use it in the Authorization: Bearer <access_token> header on all other endpoints

Token lifetime: 900 seconds (15 minutes). Repeat this call to renew it.