OAuth2.0 Password Grant Type

Hi,

I am trying to connect a 3rd party system which uses OAuth 2.0 Password Grant Type authentication, as it is not supported by Appian connected System. I have created a separate integration object to get the access code where I am passing below fields in request body.

"client_id": {client id} ,
"client_secret": {client secret},
"username": {username},
"password": {password},
"grant_type": "password"

Getting this error  "error":"invalid_request","error_description":"The grant type was not specified in the request".

I tried creating token using POSTMAN and there it was working fine. Attaching screenshot for both.

POSTMAN Response:

Appian Integration Response: