Allow to delete users while keeping log entries.

src/Controller/UserController.php

@@ -157,18 +157,6 @@ class UserController extends AdminPages\BaseAdminController
         return $this->_new($request, $em, $importer, $entity);
     }
 
-    protected function deleteCheck(AbstractNamedDBElement $entity): bool
-    {
-        if ($entity instanceof User) {
-            //TODO: Find a better solution
-            $this->addFlash('error', 'Currently it is not possible to delete a user, as this would break the log... This will be implemented later...');
-
-            return false;
-        }
-
-        return true;
-    }
-
     /**
      * @Route("/{id}", name="user_delete", methods={"DELETE"}, requirements={"id"="\d+"})
      */

src/DataTables/LogDataTable.php

@@ -188,10 +188,19 @@ class LogDataTable implements DataTableTypeInterface
             'render' => function ($value, AbstractLogEntry $context) {
                 $user = $context->getUser();
 
+                //If user was deleted, show the info from the username field
+                if ($user === null) {
+                    return sprintf(
+                        '@%s [%s]',
+                        htmlentities($context->getUsername()),
+                        $this->translator->trans('log.target_deleted'),
+                    );
+                }
+
                 return sprintf(
                     '<a href="%s">%s</a>',
                     $this->urlGenerator->generate('user_info', ['id' => $user->getID()]),
-                    $user->getFullName(true)
+                    htmlentities($user->getFullName(true))
                 );
             },
         ]);

src/Entity/LogSystem/AbstractLogEntry.php

@@ -143,10 +143,16 @@ abstract class AbstractLogEntry extends AbstractDBElement
 
     /** @var User The user which has caused this log entry
      * @ORM\ManyToOne(targetEntity="App\Entity\UserSystem\User", fetch="EAGER")
-     * @ORM\JoinColumn(name="id_user", nullable=false)
+     * @ORM\JoinColumn(name="id_user", nullable=true, onDelete="SET NULL")
      */
     protected ?User $user = null;
 
+    /**
+     * @var string The username of the user which has caused this log entry (shown if the user is deleted)
+     * @ORM\Column(type="string", nullable=false)
+     */
+    protected string $username = '';
+
     /** @var DateTime The datetime the event associated with this log entry has occured
      * @ORM\Column(type="datetime", name="datetime")
      */
@@ -203,9 +209,22 @@ abstract class AbstractLogEntry extends AbstractDBElement
     {
         $this->user = $user;
 
+        //Save the username for later use
+        $this->username = $user->getUsername();
+
         return $this;
     }
 
+    /**
+     * Retuns the username of the user that caused the event (useful if the user was deleted).
+     *
+     * @return string
+     */
+    public function getUsername(): string
+    {
+        return $this->username;
+    }
+
     /**
      * Returns the timestamp when the event that caused this log entry happened.
      */