Amazon API Gateway : response body is not transformed when the API is called via Postman?
Before the changes are externally visible, you need to Deploy the API !
The difference between Test Invoke on API Gateway Console and actual Invoke with API Gateway is the test invoke is always assuming the content-type is "application/json" and accept "application/json". You might want to pass "application/json" with the header accept when you invoke via Postman.