Fix Device model max age configuration handler (#2086)

src/AzureIoTHub.Portal.Infrastructure/ProductionAWSConfigHandler.cs

@@ -37,7 +37,7 @@ internal ProductionAWSConfigHandler(IConfiguration config)
 
         public override string StorageAccountConnectionString => throw new NotImplementedException();
 
-        public override int StorageAccountDeviceModelImageMaxAge => throw new NotImplementedException();
+        public override int StorageAccountDeviceModelImageMaxAge => this.config.GetValue(StorageAccountDeviceModelImageMaxAgeKey, 86400);
 
         public override bool UseSecurityHeaders => this.config.GetValue(UseSecurityHeadersKey, true);