code: @View(name = "by_username", map = "function(doc) { if(doc.username){ emit(doc.username, doc) } }")
      public CouchDbProfileDocument findByUsername(final String username) {
          return queryView("by_username", username).stream().findFirst().orElse(null);
      }
docs: Find profile by username.
  @param username to be searched for
  @return profile found