@Test void isOverCapacity() {
    // timeout
    assertThat(storage.isOverCapacity(ResponseTimeoutException.get())).isTrue();

    // top-level
    assertThat(storage.isOverCapacity(new RejectedExecutionException(
      "{\"status\":429,\"error\":{\"type\":\"es_rejected_execution_exception\"}}"))).isTrue();

    // re-wrapped
    assertThat(storage.isOverCapacity(
      new RejectedExecutionException("Rejected execution: No endpoints.",
        new EndpointGroupException("No endpoints")))).isTrue();

    // not applicable
    assertThat(storage.isOverCapacity(new IllegalStateException("Rejected execution"))).isFalse();
  }
See {@link HttpCallTest#unprocessedRequest()} which shows {@link UnprocessedRequestException}
are re-wrapped as {@link RejectedExecutionException}.
zipkin-storage/elasticsearch/src/test/java/zipkin2/elasticsearch/ElasticsearchStorageTest.java