Indicating that questions should allow a "Prefer not to answer" choice

[drnikko]

Problem:
Some questions like disability include a "Prefer not to answer" option as one of their choices. Including "prefer not to answer" can be statistically important - it signals that the user has seen this question and actively opted to not answer it, as opposed to possibly missing it and having an empty value as a result.

It makes sense to me to include this as a property of the question object, like the prompt. I'm wondering if "prefer-not-to-answer": "true", is sufficient to indicate to the consumer that they'll need to add that option and box to the choice list.

In the example below (and in the disability link above) Prefer not to answer exists as part of both an extended radio "boolean" - Yes, No, N/A, Prefer not to answer - and part of a longer list of options.

Note: there's a lot of work to do on this, and the scope of this issue is only how to indicate prefer not to answer. Other parts of the schema are reviewed in other issues.

Proposed solution:

         ... more stuff up here
      "a-third-kind-of-category-id?": {
             "id": "disability",
             "short-description": "This might be recommended question set wrapper text.",
             "long-description": "This might contain text about how this data could be used, external references, etc etc.",
             "questions": {
                 "do-you-have-disability": {
                   "type": "select-multiple",
                   "prompt": "Do you identify as having a disability as defined under the [Americans with Disabilities Act](https://adata.org/faq/what-definition-disability-under-ada)?",
                   "self-identify": "true",
                   "prefer-not-to-answer": "true",
                   "choices": [
                     { "id": "d-cog", "value": "cognitive", "label": "Yes, Cognitive" },
                     { "id": "d-emo", "value": "emotional", "label": "Yes, Emotional" },
                     { "id": "d-h", "value": "hearing", "label": "Yes, Hearing" },
                     { "id": "idsarehard", "value": "mental", "label": "Yes, Mental" },
                     { "id": "shouldthesebenumb", "value": "physical", "label": "Yes, Physical" },
                     { "id": "d-cog", "value": "visual", "label": "Yes, Visual" },
                     { "id": "d-cog", "value": "no", "label": "No" },
                     { "id": "d-cog", "value": "decline", "label": "Prefer not to answer" }
                     ]
                 },
                 "disability-impact-work": {
                   "type": "boolean",
                   "prompt": "Does your disability affect how you work?",
                   "self-identify": "false",
                   "does-not-apply": "true",
                   "prefer-not-to-answer": "true"
                 }

             }
         }
 .... more stuff down here