Populate the initial value using the initial expression extension for reference type

[omarismail94]

IMPORTANT: All PRs must be linked to an issue (except for extremely trivial and straightforward changes).

Fixes #1830

Description
When the Questionnaire Type is a Reference, but contains an initial expression extension that returns an ID, make this ID a reference type so that it can be displayed

Alternative(s) considered
Have you considered any alternatives? And if so, why have you chosen the approach in this PR?

No

Type
Choose one: (Bug fix | Feature | Documentation | Testing | Code health | Builds | Releases | Other)

Screenshots (if applicable)

Checklist

• I have read and acknowledged the Code of conduct.
• I have read the Contributing page.
• I have signed the Google Individual CLA, or I am covered by my company's Corporate CLA.
• I have discussed my proposed solution with code owners in the linked issue(s) and we have agreed upon the general approach.
• I have run ./gradlew spotlessApply and ./gradlew spotlessCheck to check my code follows the style guide of this project.
• I have run ./gradlew check and ./gradlew connectedCheck to test my changes locally.
• I have built and run the demo app(s) to verify my change fixes the issue and/or does not break the demo app(s).

[codecov]

Codecov Report

Merging #1831 (a2e4cde) into master (0794d2a) will increase coverage by 43.49%.
The diff coverage is 0.00%.

❗ Current head a2e4cde differs from pull request most recent head 4d2c62a. Consider uploading reports for the commit 4d2c62a to get more accurate results

@@              Coverage Diff              @@
##             master    #1831       +/-   ##
=============================================
+ Coverage          0   43.49%   +43.49%     
- Complexity        0      409      +409     
=============================================
  Files             0      160      +160     
  Lines             0     6005     +6005     
  Branches          0     1132     +1132     
=============================================
+ Hits              0     2612     +2612     
- Misses            0     2935     +2935     
- Partials          0      458      +458     

Impacted Files	Coverage Δ
...android/fhir/datacapture/mapping/ResourceMapper.kt	29.89% <0.00%> (ø)
...acapture/validation/MaxValueConstraintValidator.kt	75.00% <0.00%> (ø)
...id/fhir/datacapture/MoreQuestionnairesResponses.kt	100.00% <0.00%> (ø)
...ogle/android/fhir/sync/remote/RemoteFhirService.kt	0.00% <0.00%> (ø)
...droid/fhir/index/SearchParamDefinitionsProvider.kt	100.00% <0.00%> (ø)
...r/datacapture/views/QuestionnaireItemHeaderView.kt	82.35% <0.00%> (ø)
...ws/QuestionnaireItemAttachmentViewHolderFactory.kt	27.73% <0.00%> (ø)
...n/java/com/google/android/fhir/search/SearchDsl.kt	82.66% <0.00%> (ø)
...android/fhir/datacapture/utilities/FhirPathUtil.kt	0.00% <0.00%> (ø)
... and 151 more

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[jingtang10]

As a general comment, should we use the question type as an input when we set initial answers?

For example, IdType may be converted to either a string, or a reference, depending on the question item type. Is this something that's specified in FHIR? Is there a fixed list of allowed mappings? Or is this something we just want to do in our code.

[sevenreup]

@omarismail94 I managed to test the PR, but I found an issue where the initial expression value is not being set.
I used the same questionnaire you defined here. Still cannot get the initial value to show up