Use APM HTTP Auth to send a SOAP Message for OTP

An HTTP AAA is going to work with either a form GET/POST, Basic, or an NTML auth.

An HTTP form GET puts the user:pass in the request query string. An HTTP form POST puts the user:pass in a POST payload. The Basic and NTLM methods encode the auth into an Authorization header. The AAA allows you to add additional headers and other custom values, but that's really the limit of the flexibility. To inject an entire SOAP message in a POST, you'd necessarily need the more manual sideband approach.