Add support for all Questionnaire enableWhen operators

[rahul1]

Right now, when evaluating the Questionnaire.item.enableWhen logic, we assume that the user is checking for equality. In the example below, I'd also like to check for existence, which is not currently handled.

Would also be nice to for booleans to default eval to "false" if they don't exist, so two conditions are not needed

{
  "resourceType": "Questionnaire",
  "name": "Merge Duplicate Patients",
  "status": "active",
  "item": [
    {
      "id": "id-15",
      "linkId": "g3",
      "type": "group",
      "text": "Disable Merge ",
      "item": [
        {
          "id": "id-23",
          "linkId": "q1",
          "type": "display",
          "text": "Check this box is the Patient records ARE NOT a match. This will add each Patient to the other's \"Do Not Match\" list"
        },
        {
          "id": "id-16",
          "linkId": "disableMerge",
          "type": "boolean",
          "text": "*Do not Merge these records*"
        }
      ]
    },
    {
      "id": "id-17",
      "linkId": "g5",
      "type": "group",
      "text": "Merging Patients",
      "item": [
        {
          "id": "id-18",
          "linkId": "replaceName",
          "type": "boolean",
          "text": "Merge names?\nIf selected, this will add the source patient's name to the target's list of names"
        },
        {
          "id": "id-19",
          "linkId": "replaceAddress",
          "type": "boolean",
          "text": "Merge Addresses?\nIf selected, this will add the source patient's address to the target's list of addresses"
        },
        {
          "id": "id-20",
          "linkId": "replaceData",
          "type": "boolean",
          "text": "Replace birthdate?\nIf selected, this will REPLACE the target patient's birthdate with the source patient's birthdate"
        }
      ],
      "enableWhen": [
        {
          "question": "disableMerge",
          "operator": "=",
          "answerBoolean": false
        },
        {
          "question": "disableMerge",
          "operator": "exists",
          "answerBoolean": false
        }
      ],
      "enableBehavior": "any"
    },
    {
      "id": "id-21",
      "linkId": "g9",
      "type": "group",
      "text": "Deleting Source Patient",
      "item": [
        {
          "id": "id-22",
          "linkId": "deleteSource",
          "type": "boolean",
          "text": "Would you like to delete the source patient after merging?"
        }
      ],
      "enableWhen": [
        {
          "question": "disableMerge",
          "operator": "=",
          "answerBoolean": false
        },
        {
          "question": "disableMerge",
          "operator": "exists",
          "answerBoolean": false
        }
      ],
      "enableBehavior": "any"
    }
  ],
  "subjectType": [
    "RiskAssessment"
  ],
  "title": "Merge Duplicate Patients",
  "id": "02055bc0-d0c9-4441-a6c4-94e490336f99",
  "meta": {
    "versionId": "68bbe973-2ca8-48c8-9ee7-7e57e3446485",
    "lastUpdated": "2023-08-17T17:37:12.410Z",
    "author": {
      "reference": "Practitioner/bda1c932-8e56-4c10-92fa-bbbb3fbe4b03",
      "display": "Rahul Agarwwal"
    },
    "project": "b65c0057-5926-4d59-9486-1039125784ac",
    "compartment": [
      {
        "reference": "Project/b65c0057-5926-4d59-9486-1039125784ac"
      }
    ]
  }
}

[lazyfuhrer]

Hey I'd like to work in this @rahul1