Remove the Task.Run from AzureKeyVaultTokenSigningService about identityserver.contrib.azurekeyvaulttokensigningservice

[MattCotterellNZ]

Makes sense. We still need to keep the non-async method there since we need to override the SignatureProvider's Sign() method, but there shouldn't be any harm in adding an additional SignAsync() (and VerifyAsync()) method too. Does that sound right?

[omerlh]

I don't see the benefit of using this interface, it might be better to create a dedicate interface for that...

[MattCotterellNZ]

I think this was partly to provide support for people who may not be using IdentityServer but still want to use parts of this library to sign JWTs using Azure Key Vault, but this is probably misguided and should probably be well out of scope (or in a different NuGet package altogether). I'll keep this in mind before release and look into it in a bit more depth, it may be appropriate to break away from this interface.