internal Mappings Remove(Mapping mapping, out bool wasCreated)
{
wasCreated = Created.Contains(mapping);
var created = Created.Contains(mapping) ? Created.Except(new[] { mapping }).ToArray() : Created;
var pending = Pending.Contains(mapping) ? Pending.Except(new[] { mapping }).ToArray() : Pending;
var failed = Failed.Contains(mapping) ? Failed.Except(new[] { mapping }).ToArray() : Failed;
return(new Mappings(created, pending, failed));
}