Send an email when a workflow is send to an external

- create an event subscriber to catch the workflow which arrive to a "sentExternal" step;
- add a messenger's message to handle the generation of the email;
- add a simple message, and a simple controller for viewing the document
- add dedicated tests

src/Bundle/ChillMainBundle/Entity/Workflow/EntityWorkflowSend.php

@@ -124,6 +124,16 @@ class EntityWorkflowSend implements TrackCreationInterface
         return $this->uuid;
     }
 
+    public function getExpireAt(): \DateTimeImmutable
+    {
+        return $this->expireAt;
+    }
+
+    public function getViews(): Collection
+    {
+        return $this->views;
+    }
+
     public function increaseErrorTrials(): void
     {
         $this->numberOfErrorTrials = $this->numberOfErrorTrials + 1;