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":"a0d8c471-fa15-404a-b564-65f25dea406c"}

POST Request:
HTTP Code: 401
Response: {"status_code":"401","status_message":"Unknown Merchant server_key/id","id":"a1735b14-91a6-41ea-b344-55a4aac27ee1"}