In externally visible method 'string IdempotencyStore.CalculateIdempotencyKey(OrderIdComponents orderId, string orderJson)', validate parameter 'orderId' is non-null before using it. If appropriate, throw an ArgumentNullException when the argument is null or add a Code Contract precondition asserting non-null argument. [/home/runner/work/OpenActive.Server.NET/OpenActive.Server.NET/server/OpenActive.Server.NET/OpenActive.Server.NET.csproj]