Make AuthContext constructor public

[jtattermusch]

to enable creating instances of AuthContext in grpc-dotnet.

Fixes grpc/grpc-dotnet#76.

[jtattermusch]

CC @JamesNK @JunTaoLuo

[jtattermusch]

AuthProperty still has a private constructor - we'll need to look into that.

[JamesNK]

re: private constructor

The constructor is private but there is a static Create method:

grpc/src/csharp/Grpc.Core.Api/AuthProperty.cs

Lines 85 to 91 in 5268858

	public static AuthProperty Create(string name, byte[] valueBytes)
	{
	GrpcPreconditions.CheckNotNull(valueBytes);
	var valueCopy = new byte[valueBytes.Length];
	Buffer.BlockCopy(valueBytes, 0, valueCopy, 0, valueBytes.Length);
	return new AuthProperty(name, valueCopy);
	}

[jtattermusch]

re: private constructor

The constructor is private but there is a static Create method:

grpc/src/csharp/Grpc.Core.Api/AuthProperty.cs

Lines 85 to 91 in 5268858

public static AuthProperty Create(string name, byte[] valueBytes)
{
GrpcPreconditions.CheckNotNull(valueBytes);
var valueCopy = new byte[valueBytes.Length];
Buffer.BlockCopy(valueBytes, 0, valueCopy, 0, valueBytes.Length);
return new AuthProperty(name, valueCopy);
}

Ah, somehow I completely missed that. Thanks for pointing that out.

[jtattermusch]

Known failures: #18477