[BUG] Using`$ now()` in Mapping throws an error

[vesnushka]

Describe the bug We faced en error in extracting the questionnaire due to the use of $ now() in Mapping

Severity Critical

Steps to reproduce the behavior:

1. The Mapping example with $ now() Note: the use of variables is required to reproduce the error

   body:
   $let:
   patientId: >-
     $
     fhirpath("QuestionnaireResponse.repeat(item).where(linkId='patientId').answer.value.string").0
   $body:
   type: transaction
   entry:
     - request:
         url: /Observation
         method: POST
       resource:
         code:
           coding:
             - code: 29463-7
               system: http://loinc.org
               display: Body weight
         value:
           Quantity:
             unit: kg
             value: 80
         status: final
         subject:
           id: $ patientId
           resourceType: Patient
         effective:
           dateTime: $ now()
         resourceType: Observation
   resourceType: Bundle
   id: test-now-extract
   resourceType: Mapping

2. $debug returns correct result

   
   POST /Mapping/test-now-extract/$debug
   Content-Type: text/yaml

patientId: ede14f63-fffa-4ed0-aed8-b5b4f34f0055

Result:

type: transaction entry:

• request: url: /Observation method: POST resource: code: coding:
  • code: 29463-7 system: http://loinc.org display: Body weight value: Quantity: unit: kg value: 80 status: final effective: dateTime: 2023-03-20T14:35:59.726Z resourceType: Observation resourceType: Bundle

3. But $apply returns the error

POST /Mapping/test-now-extract/$apply
Content-Type: text/yaml

patientId: ede14f63-fffa-4ed0-aed8-b5b4f34f0055

The answer

resourceType: OperationOutcome
...
text:
  status: generated
  div: >-
    Transaction failed at entry[0]. Response status is 422. Response body is
    {"resourceType":"OperationOutcome","text":{"status":"generated","div":"Invalid
    resource"},"issue":[{"severity":"fatal","code":"invalid","expression":["Observation.effective.dateTime"],"diagnostics":"expected
    type of string"}]}.
issue:
  - severity: fatal
    code: invalid
    diagnostics: expected type of string
    expression:
      - Observation.effective.dateTime

Expected behavior $apply should return FHIR dateTime with no error

Versions:

• Aidbox image version: v:2302.b6d04231