API Gateway endpoint Authentication from ServiceNow

Hi,

Have a few Services run via API Gateway in multiple AWS accounts. I am trying to invoke API Gateway from the ServiceNow platform, so trying to figure out how can I authenticate API Gateway without storing credentials locally into ServiceNow. There are some limitations on the ServiceNow platform as below:

• The ServiceNow platform supports only Native JavaScript and cannot import any external packages like aws_auth etc to generate signatures to authenticate API.
• I do not want to write a whole function to generate Signature4 into ServiceNow which requires a store access key and secret_key to store into ServiceNow.
• Can we use the IAM role to authenticate API from the external app?

Please suggest on best approach to avoid regular kyes/password rotation, storing locally into ServiceNow.