Please create a small example for a auth_callout service created in C#

[ploef]

Hi,

I try to implement a auth_callout service created with c#. I have it working now except for the signing part. the auth_callout configuration has the xkey set (created using nsc generate nkey --curve).
I did find an example created in go (https://github.com/ConnectEverything/nats-by-example/blob/main/examples/auth/callout/cli/service/main.go). In that example, on line 52, the keypair is created for the xkey (SXA......). The .NET package also has the possibility with the "FromSeed" method. This does work for the issuerKey, but not for the xkey (Invalid Public Prefix Byte)