Testing with exact Midtrans format:
Server Key: Mid-server-VWcHi6YMhvY0l1IBlHgzm1K7
Merchant ID: G689699337
Authorization Header: Basic TWlkLXNlcnZlci1WV2NIaTZZTWh2WTBsMUlCbEhnem0xSzc6
HTTP Code: 401
Response: {"status_code":"401","status_message":"Unknown Merchant server_key/id","id":"87e120ed-1fc8-433e-bc43-1ff9e730479a"}

POST Request:
HTTP Code: 401
Response: {"status_code":"401","status_message":"Unknown Merchant server_key/id","id":"54f95b6a-172f-4600-b94a-0e4272a09f74"}