Add POST request handling in InvokeRecActionCommandHandler

Previously, the handling of HTTP POST requests in the
InvokeRecActionCommandHandler class was not implemented.
This commit adds the necessary code to handle POST requests
by using the http.PostAsync method. The POST request is sent
to the specified action.EndpointUri with null content and a
cancellation token. This change ensures that POST operations
are now properly executed within the command handler.

src/ReC.Application/RecActions/Commands/InvokeRecActionCommand.cs

@@ -34,7 +34,7 @@ public class InvokeRecActionCommandHandler(ISender sender) : IRequestHandler<Inv
                 }
                 case "POST":
                 {
-                    // Handle POST
+                    using var response = await http.PostAsync(action.EndpointUri, null, cancel);
                     break;
                 }
                 case "PUT":