code: private Result sessionInfo() {
  
          Map<String, Object> dataEachSession = new HashMap<>();
          for (Map.Entry<String, StatsStorage> entry : knownSessionIDs.entrySet()) {
              String sid = entry.getKey();
              StatsStorage ss = entry.getValue();
              Map<String, Object> dataThisSession = sessionData(sid, ss);
              dataEachSession.put(sid, dataThisSession);
          }
          return Results.ok(asJson(dataEachSession)).as("application/json");
      }
docs: Display, for each session: session ID, start time, number of workers, last update
  @return info for each session as JSON