Retry transient errors

[ohadschn]

I recently encountered the following callstack:

ACMESharp.AcmeClient+AcmeWebException: Unexpected error
 +Response from server:
	+ Code: InternalServerError
	+ Content: {
  "type": "urn:acme:error:serverInternal",
  "detail": "Error creating new authz",
  "status": 500
} ---> System.Net.WebException: The remote server returned an error: (500) Internal Server Error.
   at System.Net.HttpWebRequest.GetResponse()
   at ACMESharp.AcmeClient.RequestHttpPost(Uri uri, Object message)
   --- End of inner exception stack trace ---
   at ACMESharp.AcmeClient.AuthorizeIdentifier(String dnsIdentifier)

Looking up this error, it seems like a known transient failure that should be retried (which indeed worked). Perhaps such retries could be incorporated into the ACME Client?