code: func (api UsersAPI) LookupIyoID(w http.ResponseWriter, r *http.Request) {
  	id := mux.Vars(r)["identifier"]
  	azp, _ := context.Get(r, "client_id").(string)
  
  	mgr := iyoid.NewManager(r)
  	// Get the identifier object for the id and azp
  	idObj, err := mgr.GetByIDAndAZP(id, azp)
  	if err != nil && !db.IsNotFound(err) {
  		handleServerError(w, "listing user iyoids", err)
  		return
  	}
  
  	// Report if we didn't find anything
  	if db.IsNotFound(err) {
  		http.Error(w, http.StatusText(http.StatusNotFound), http.StatusNotFound)
  		return
  	}
  
  	// If the identifier belongs to another azp report that we didn't find something for this user either
  	if idObj.Azp != azp {
  		http.Error(w, http.StatusText(http.StatusNotFound), http.StatusNotFound)
  		return
  	}
  
  	// Only reveal this id in the response object
  	for i, sid := range idObj.IyoIDs {
  		if sid == id {
  			idObj.IyoIDs = idObj.IyoIDs[i : i+1]
  		}
  	}
  
  	w.Header().Set("Content-Type", "application/json")
  	w.WriteHeader(http.StatusOK)
  	json.NewEncoder(w).Encode(idObj)
  }
docs: // LookupIyoID is the handler for GET /users/identifiers/{identifier}
  // Lookup the username behind an iyo id