Add Http Response Behavior to answer synchronously using the HttpResponse Activity (#5446)

* Update WriteHttpResponse.cs to call response.CompleteAsync()

* Add options in HttpActivityOptions

---------

Co-authored-by: Ciaran ODonnell <wannabedeveloper@live.com>
Co-authored-by: Jérémie DEVILLARD <jdevillard@users.noreply.github.com>

src/modules/Elsa.Http/Activities/WriteHttpResponse.cs

@@ -10,6 +10,8 @@ using Elsa.Workflows.UIHints;
 using Elsa.Workflows.Exceptions;
 using Elsa.Workflows.Models;
 using Microsoft.AspNetCore.Http;
+using Microsoft.Extensions.Options;
+using Elsa.Http.Options;
 
 namespace Elsa.Http;
 
@@ -133,7 +135,12 @@ public class WriteHttpResponse : Activity
                     await response.WriteAsync("The response includes a type that cannot be serialized.");
                 }
             }
-        }
+        }
+
+        //Check if the configuration is set to flush immediatly the response to the caller.
+        var options = context.GetRequiredService<IOptions<HttpActivityOptions>>();
+        if (options.Value.WriteHttpResponseSynchronously)
+            await response.CompleteAsync();
 
         // Complete activity.
         await context.CompleteActivityAsync();
@@ -144,4 +151,4 @@ public class WriteHttpResponse : Activity
         : content is string
             ? "text/plain"
             : "application/json";
-}
+}

src/modules/Elsa.Http/Options/HttpActivityOptions.cs

@@ -35,5 +35,11 @@ public class HttpActivityOptions
         "text/html",
         "text/json", 
         "text/xml",
-    };
+    };
+
+    /// <summary>
+    /// A boolean to opt-in if you want to call CompleteAsync() in the HttpResponse Activity
+    /// and not waiting for the end of the HttpMiddleware. 
+    /// </summary>
+    public Boolean WriteHttpResponseSynchronously { get; set; } = false;
 }