Logic fix for changed external behavour (#21)

* ValidateOrderAsync Exception info null guard

* Log OrderInvalidException before throwing it

* bugfix: One valid challenge is enough

don't wait for all to resolve. Issue discussed in #20

* Remove trace logs

src/FluffySpoon.AspNet.LetsEncrypt/LetsEncryptRenewalService.cs

@@ -1,6 +1,5 @@
 using System;
 using System.Collections.Generic;
-using System.IO;
 using System.Linq;
 using System.Security.Cryptography;
 using System.Security.Cryptography.X509Certificates;
@@ -273,31 +272,32 @@ private async Task ValidateOrderAsync(string[] domains, IOrderContext order)
 
 				var challengeExceptions = nonNullChallengeValidationResponses
 					.Where(x => x.Status == ChallengeStatus.Invalid)
-					.Select(x => new Exception($"{x.Error.Type}: {x.Error.Detail} (challenge type {x.Type})"))
+					.Select(x => new Exception($"{x.Error?.Type ?? "errortype null"}: {x.Error?.Detail ?? "null errordetails"} (challenge type {x.Type ?? "null"})"))
 					.ToArray();
 
-				if (challengeExceptions.Length > 0)
+				if (challengeExceptions.Length > 0) 
 					throw new OrderInvalidException(
 						"One or more LetsEncrypt orders were invalid. Make sure that LetsEncrypt can contact the domain you are trying to request an SSL certificate for, in order to verify it.",
 						new AggregateException(challengeExceptions));
+
 			}
 			finally
 			{
 				await _persistenceService.DeleteChallengesAsync(challengeDtos);
 			}
 		}
 
-		private static async Task<Challenge[]> ValidateChallengesAsync(IEnumerable<IChallengeContext> challengeContexts)
+		private async Task<Challenge[]> ValidateChallengesAsync(IEnumerable<IChallengeContext> challengeContexts)
 		{
 			var challenges = await Task.WhenAll(
 								challengeContexts.Select(x => x.Validate()));
 
 			while (true)
 			{
-				if (!challenges.Any(x => x.Status == ChallengeStatus.Pending || x.Status == ChallengeStatus.Processing))
+				if (challenges.Any(x => x.Status == ChallengeStatus.Valid) || challenges.All(x => x.Status == ChallengeStatus.Invalid))
 					break;
-
-				await Task.Delay(1000);
+                
+                await Task.Delay(1000);
 				challenges = await Task.WhenAll(challengeContexts.Select(x => x.Resource()));
 			}