code: protected RejectedExecutionHandler getRejectedExecutionHandler(Dsn dsn) {
          String overflowName = ASYNC_QUEUE_OVERFLOW_DEFAULT;
          String asyncQueueOverflowOption = Lookup.lookup(ASYNC_QUEUE_OVERFLOW_OPTION, dsn);
          if (!Util.isNullOrEmpty(asyncQueueOverflowOption)) {
              overflowName = asyncQueueOverflowOption.toLowerCase();
          }
  
          RejectedExecutionHandler handler = REJECT_EXECUTION_HANDLERS.get(overflowName);
          if (handler == null) {
              String options = Arrays.toString(REJECT_EXECUTION_HANDLERS.keySet().toArray());
              throw new RuntimeException("RejectedExecutionHandler not found: '" + overflowName
                  + "', valid choices are: " + options);
          }
  
          return handler;
      }
docs: Handler for tasks that cannot be immediately queued by a {@link ThreadPoolExecutor}.
  
  @param dsn Sentry server DSN which may contain options.
  @return Handler for tasks that cannot be immediately queued by a {@link ThreadPoolExecutor}.