review: fix stuffs on socialAction and socialIssue filters:

* filters call static entity method
* add renderString option to manage add_children
* add tests on new entity method getDescendantsWithThisFor..()
* rename function in repository
* rename 'Select2..' classes by 'Pick..' and replace all occurences

src/Bundle/ChillPersonBundle/Entity/SocialWork/SocialIssue.php

@@ -215,6 +215,23 @@ class SocialIssue
         return $descendants;
     }
 
+    /**
+     * @param Collection|SocialIssue[] $socialIssues
+     * @return Collection
+     */
+    public static function getDescendantsWithThisForIssues(Collection $socialIssues): Collection
+    {
+        $unique = [];
+
+        foreach ($socialIssues as $issue) {
+            foreach ($issue->getDescendantsWithThis() as $child) {
+                $unique[spl_object_hash($child)] = $child;
+            }
+        }
+
+        return new ArrayCollection(array_values($unique));
+    }
+
     public function getId(): ?int
     {
         return $this->id;
@@ -267,6 +284,11 @@ class SocialIssue
         return null !== $this->parent;
     }
 
+    public function hasChildren(): bool
+    {
+        return 0 < $this->getChildren()->count();
+    }
+
     /**
      * Recursive method which return true if the current $issue is a descendant
      * of the $issue given in parameter.