Better error messages for bad conditional references

[lmsurpre]

Is your feature request related to a problem? Please describe.
Resolving conditional references as part of transaction bundle processing was implemented under #1329

When the conditional reference cannot be resolved (no matches) or resolves to multiple target resources, the server will now reject the create/update.

However, the error message is a fairly generic "conditional reference could not be resolved" or "conditional reference resolves to more than one resource" (or something like that).

Instead, it would be nice if we could include the path to the offending conditional reference (and/or the conditional reference’s value itself).

Describe the solution you'd like
At minimum: An expression in the OperationOutcomeIssue that specifies the path to the offending conditional reference

Bonus: the url of the conditional reference that failed in the detail message

Describe alternatives you've considered

Acceptance Criteria

1. GIVEN a transaction bundle with a condition reference
   AND the conditional reference is bogus
   WHEN the bundle is posted
   THEN an operation outcome is returned
   AND it contains an issue that includes a path to the bogus conditional reference

2. GIVEN a transaction bundle with a condition reference
   AND the conditional reference resolves to multiple resources
   WHEN the bundle is posted
   THEN an operation outcome is returned
   AND it contains an issue that includes a path to the bogus conditional reference

Additional context

[kmbarton423]

Confirmed issues created for conditional references in a transaction bundle for the following cases:

• reference does not resolve
• reference resolves to multiple
• reference search is invalid

in all cases the resulting issue contains an expression indicating the location (Bundle.entry[x])
confirmed varied location of failure within the bundle were represented accurately

example:
{ "resourceType": "OperationOutcome", "id": "ac-11-0-2-1aafb23b-2ef4-4798-bb94-8fc5fe053f66", "issue": [ { "severity": "fatal", "code": "not-found", "details": { "text": "Error resolving conditional reference: search 'Patient?_id=PatientBogus' returned no results" }, "expression": [ "Bundle.entry[0]" ] } ] }