Only select QuestionnaireItem with 'page' extension as page

[LZRS]

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

Fixes #2568

Description
Change getQuestionnairePages to only return questionnaire pages from QuestionnaireItems that have extension

        {
          "url": "http://hl7.org/fhir/StructureDefinition/questionnaire-itemControl",
          "valueCodeableConcept": {
            "coding": [
              {
                "system": "http://hl7.org/fhir/questionnaire-item-control",
                "code": "page",
                "display": "Page"
              }
            ]
          }
        }

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

Type
Bug fix

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).

[MJ1998]

We need to include contiguous set of items not with page extension into another page.

"If there are items at the same level as a 'page' group that are listed before the 'page' group, they will be treated as a separate page"
Reference - https://build.fhir.org/ig/HL7/fhir-extensions//CodeSystem-questionnaire-item-control.html

So if the questionnaire looks like -

{
  itemWithNoPageExtension1, 
  itemWithPageExtension2, // have nested items
  itemWithPageExtension3,
  itemWithNoPageExtension4,
  itemWithNoPageExtension5,
  itemWithNoPageExtension6,
  itemWithPageExtension7,
}

The pages would look like following:-

{
  page1: {
  	itemWithNoPageExtension1,
  },
  page2: {
  	itemWithPageExtension2
  },
  page3: {
  	itemWithPageExtension3
  },
  page4: {
  	itemWithNoPageExtension4,
  	itemWithNoPageExtension5,
  	itemWithNoPageExtension6
  },
  page5: {
  	itemWithPageExtension7
  }
}

[MJ1998]

How are these 2 different ?

[LZRS]

The second one is using index as defined and set in https://github.com/google/android-fhir/blob/10165589c4e7617b3bdd3a426d037f639c135342/datacapture/src/main/java/com/google/android/fhir/datacapture/QuestionnaireViewModel.kt#L933C11-L933C16

While the previous one was using index of the page from pages list, although they'll essentially be the same if our pages are contigous as you mentioned in your comment

[LZRS]

We need to include contiguous set of items not with page extension into another page.

"If there are items at the same level as a 'page' group that are listed before the 'page' group, they will be treated as a separate page" Reference - https://build.fhir.org/ig/HL7/fhir-extensions//CodeSystem-questionnaire-item-control.html

So if the questionnaire looks like -

{
  itemWithNoPageExtension1, 
  itemWithPageExtension2, // have nested items
  itemWithPageExtension3,
  itemWithNoPageExtension4,
  itemWithNoPageExtension5,
  itemWithNoPageExtension6,
  itemWithPageExtension7,
}

The pages would look like following:-

{
  page1: {
  	itemWithNoPageExtension1,
  },
  page2: {
  	itemWithPageExtension2
  },
  page3: {
  	itemWithPageExtension3
  },
  page4: {
  	itemWithNoPageExtension4,
  	itemWithNoPageExtension5,
  	itemWithNoPageExtension6
  },
  page5: {
  	itemWithPageExtension7
  }
}

Ah okay, makes sense. Probably we'd then need to make changes to our questionnaires, thanks