Testing with exact Midtrans format:
Server Key: Mid-server-VWcHi6YMhvY0l1IBlHgzm1K7
Merchant ID: G689699337
Authorization Header: Basic TWlkLXNlcnZlci1WV2NIaTZZTWh2WTBsMUlCbEhnem0xSzc6
HTTP Code: 401
Response: {"error":"Unauthorized"}

POST Request:
HTTP Code: 401
Response: {"error":"Unauthorized"}