Add support for message inspectors in the callback channel

[lukasz-zoglowek]

Describe the bug
.NET Core version of WCF is missing CallbackDispatchRuntime.MessageInspectors API on ClientRuntime class and IDispatchMessageInspector interface.

To Reproduce
In legacy .NET we have following code for logging messages (outgoing and incoming messages from callback channel)

var messageLogger = new MessageLogger();
clientRuntime.MessageInspectors.Add(messageLogger);
clientRuntime.CallbackDispatchRuntime.MessageInspectors.Add(messageLogger);
clientRuntime.ClientMessageInspectors.Add(messageLogger);


public class MessageLogger : IClientMessageInspector, IDispatchMessageInspector
{
    public void AfterReceiveReply(ref Message reply, object correlationState)
    {
        // Log outgoing messages
    }

    public object AfterReceiveRequest(ref Message request, IClientChannel channel, InstanceContext instanceContext)
    {
        // Log incoming messages from callback channel
    }
}

[HongGit]

@imcarolwang can you please work on this implementation at your earliest convenience?

[tapizquent]

Having access to AfterReceiveRequest and BeforeSendReply from IDispatchMessageInspector is critical to ensuring messages can be modified.

Is there any workaround to using BeforeSendReply with the current exposed APIs?

[mconnew]

@tapizquent, there is a hideous workaround. You can create your own custom bindingelement and insert it in the channel stack at the top. It would see every message coming in and every message going out, including client initiated requests. An IDispatchMessageInspector is a lot easier as it only gets called for callback methods. We're going to add this for the .NET 6 release timeframe, but you can keep using it on your current version of .NET that you are using as WCF doesn't depend on the latest .NET release.

[mconnew]

This will be available in RC2

[StephenBonikowsky]

@mconnew is there a merged PR we can link this to?

[mconnew]

The PR was #4699

[StephenBonikowsky]

Thanks!