Adds a chief complaint to an interview.

The client should not expect that an interpretation will be returned for all user-generated complaints. The AI will do its best to interpret the query, but it is not guaranteed to succeed in finding appropriate interpretation matches.

In instances where no interpretations are returned, the user should be asked to submit a new query. If a complaint is accepted while the interview is in the "protocol" or "differential" mode, the interview will be reset to the "input" mode.