Currently harness snow connector doc says API key is a supported authentication mechanism with service now. But I have confirmed with support that it is not a supported option. Documentation is in error.

RFE: Support API Key for ServiceNow connector

Pls note when using API Key the credential is passed as Header or Query parameter. Header is preferred.

Pls reference ticket https://support.harness.io/hc/en-us/requests/90886?page=1

as well as slack Question