feature #20787 [Workflow] Added an entered event (Padam87)

This PR was submitted for the 3.2 branch but it was merged into the 3.3-dev branch instead (closes #20787).

Discussion
----------

[Workflow] Added an entered event

| Q             | A
| ------------- | ---
| Branch?       |  3.2
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #20774 (partially) ; #21433
| License       | MIT
| Doc PR        | -

Commits
-------

7a562bd [Workflow] Added an entered event

src/Symfony/Component/Workflow/Tests/WorkflowTest.php

@@ -239,6 +239,10 @@ public function testApplyWithEventDispatcher()
             'workflow.workflow_name.enter',
             'workflow.workflow_name.enter.b',
             'workflow.workflow_name.enter.c',
+            'workflow.entered',
+            'workflow.workflow_name.entered',
+            'workflow.workflow_name.entered.b',
+            'workflow.workflow_name.entered.c',
             // Following events are fired because of announce() method
             'workflow.guard',
             'workflow.workflow_name.guard',

src/Symfony/Component/Workflow/Workflow.php

@@ -140,6 +140,8 @@ public function apply($subject, $transitionName)
 
             $this->markingStore->setMarking($subject, $marking);
 
+            $this->entered($subject, $transition, $marking);
+
             $this->announce($subject, $transition, $marking);
         }
 
@@ -270,6 +272,22 @@ private function enter($subject, Transition $transition, Marking $marking)
         }
     }
 
+    private function entered($subject, Transition $transition, Marking $marking)
+    {
+        if (null === $this->dispatcher) {
+            return;
+        }
+
+        $event = new Event($subject, $marking, $transition);
+
+        $this->dispatcher->dispatch('workflow.entered', $event);
+        $this->dispatcher->dispatch(sprintf('workflow.%s.entered', $this->name), $event);
+
+        foreach ($transition->getTos() as $place) {
+            $this->dispatcher->dispatch(sprintf('workflow.%s.entered.%s', $this->name, $place), $event);
+        }
+    }
+
     private function announce($subject, Transition $initialTransition, Marking $marking)
     {
         if (null === $this->dispatcher) {