Support HTTP request body in InvokeRecActionCommandHandler

Added logic to handle non-null `request.Body` in HTTP requests.
Introduced a `StringContent` object to encapsulate the body
content and assigned it to the `Content` property of the
HTTP request. This ensures that the request body is included
when sending data to the specified endpoint.

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

@@ -40,6 +40,12 @@ public class InvokeRecActionCommandHandler(
             .ToHttpMethod()
             .ToHttpRequestMessage(request.EndpointUri);
 
+        if(request.Body is not null)
+        {
+            using var reqBody = new StringContent(request.Body);
+            httpReq.Content = reqBody;
+        }
+
         using var response = await http.SendAsync(httpReq, cancel);
         var body = await response.Content.ReadAsStringAsync(cancel);
         var headers = response.Headers.ToDictionary();