Which fields are returned in a response?
Many methods in the Stack Exchange API return complicated responses.
/questions?answers=true&comments=true&... returns some set of questions (which may have comments) with answers (which may, themselves, have comments) and
any returned question, answer, or comment will likely contain some information on a user. Parsing this data can be complicated by uncertainty about which fields
will be returned.
To clarify, unless contra-indicated by a parameter (as body, comments, and answers often are), the API will make a best effort attempt at providing
a field. If data is not available, the field will be omitted from the return. The API will never return
null, the field will simply not be