Form-data Payload format for http-connector

Hi, I have mostly done apigee calls mostly internal systems using http-connectors and the payload I have used will be in this format:
var payload = {
“client_id” : “UN3qQVO9pHN644K5HUF6z8bKJIO4UEcK”,
“client_secret”: “LwaYGLlkcSxevBfl”,
“grant_type”: “client_credentials”
};

JSON.stringify(payload);

I am stuck in making an API call to external system, the API is created using DEX and payload is expected in form-data. Any suggestion about how to create a payload which expects in form-data format?

any success?