Richard chen

@RickWinter Thoughts?

@maffin-sa @tlund101 passing string `\x00` to labelFilter should work, it represents NULL char ASCII in Golang. It's indeed confusion leading, [LabelFilter.Null](https://learn.microsoft.com/en-us/dotnet/api/microsoft.extensions.configuration.azureappconfiguration.labelfilter.null?view=azure-dotnet#microsoft-extensions-configuration-azureappconfiguration-labelfilter-null) in .net SDK is also this value, we should...