Update consent - http error codes

[InteropAdmin]

https://nhsconnect.github.io/FHIR-NOO-API/build_consent_restful.html

What does successful URL submission mean?

Surely there could be a 404?

[dxh73]

Changed 'successful URL submission' to 'successful HTTP POST'

In theory, there should never be a 404 error ( as long as the spine app works), but this code should be documented on the slim chance something does go wrong. Now added.