[FA-5] Adds image support with proper S3 upload and replacement after upload

FictionArchive.Service.NovelService/Services/SourceAdapters/Novelpia/NovelpiaAuthMessageHandler.cs

@@ -52,10 +52,15 @@ public class NovelpiaAuthMessageHandler : DelegatingHandler
             var response = await _httpClient.SendAsync(loginMessage);
             using (var streamReader = new StreamReader(response.Content.ReadAsStream()))
             {
-                if (streamReader.ReadToEnd().Contains(LoginSuccessMessage))
+                var message = await streamReader.ReadToEndAsync();
+                if (message.Contains(LoginSuccessMessage))
                 {
                     _cache.Set(CacheKey, loginKey);
                 }
+                else
+                {
+                    throw new Exception("An error occured while retrieving the login key. Message: " + message);
+                }
             }
         }