Add success_handler to give subclass control over success (#338)

* Add success_handler to give subclass control over success

- For example, retaining completed request and mark them for completion instead of deleting them.

Co-authored-by: Maher Hawash <gmhawash@gmail.com>

lib/queue_classic/worker.rb

@@ -111,7 +111,7 @@ def process(queue, job)
       finished = false
       begin
         call(job).tap do
-          queue.delete(job[:id])
+          handle_success(queue, job)
           finished = true
         end
       rescue StandardError, ScriptError, NoMemoryError => e
@@ -139,6 +139,10 @@ def call(job)
       receiver.send(message, *args)
     end
 
+    def handle_success(queue, job)
+      queue.delete(job[:id])
+    end
+
     # This method will be called when a StandardError, ScriptError or
     # NoMemoryError is raised during the execution of the job.
     def handle_failure(job,e)