@Override
  public String toString() {
    return "RetryStrategyLibrary{" +
        "retryMappings=" + retryMappings +
        ", defaultRetryStrategy=" + defaultRetryStrategy +
        '}';
  }
Returns the best {@link RetryStrategy} for a given Throwable. If there are no matches, returns
the default RetryStrategy.

Right now it just looks at the message in the Throwable and tries to find a matching regex in
its internal library.  Later on it will use more and more of the Throwable to make a decision.
portability-types-transfer/src/main/java/org/datatransferproject/types/transfer/retry/RetryStrategyLibrary.java