Bring support of conditional updates into alignment with the R4 spec

[dmuylwyk]

Describe the bug

Support for conditional updates is not in alignment with the R4 spec.

R4 conditional updates should issue a 400 where one match is found, and a resource ID is provided but does not match the resource found. Instead, we are simply ignoring resource IDs in the body of the resource (in line with the STU3 spec).

We presently support the STU3 spec for conditional updates:

• http://hl7.org/fhir/STU3/http.html#cond-update

Compare with the R4 spec:

• http://hl7.org/fhir/http.html#cond-update

Please bring support of conditional updates into alignment with the R4 spec.

To Reproduce

Steps to reproduce the behavior:

1. POST a resource to the repository as a create operation. Note the server-assigned resource ID.
2. POST a Bundle of type transaction that includes an entry with a conditional update operation for the same resource. Ensure this entry includes a resource ID that differs from the server-assigned resource ID in step 1 above.

Observed behavior

The resource is conditionally updated without issue.

Expected behavior

The operation should result in a 400.

Cc. @jamesagnew, since we just talked about this. A letter with a vague threat of consequences should this not be resolved in a reasonable amount of time has been issued to the mayor.