Add owner organization and owner user to audits

- Rename the audit actor columns user_type/user_id to actor_type/actor_id
- Add owner_organization_id and owner_user_id to the audits table as
  foreign keys with cascade on delete, so that the audits of an
  organization or user are deleted together with it. The indexes and
  foreign keys are created without blocking writes on the large table.
- Fill the owner columns for new audits via CustomAuditable. Organizations
  and users no longer record their own deletion audit, since it would
  reference the already deleted owner.

app/Models/Concerns/CustomAuditable.php

@@ -4,6 +4,7 @@ declare(strict_types=1);
 
 namespace App\Models\Concerns;
 
+use Illuminate\Support\Facades\Config;
 use OwenIt\Auditing\Auditable;
 
 trait CustomAuditable
@@ -19,4 +20,62 @@ trait CustomAuditable
     {
         $this->auditEvents = [];
     }
+
+    /**
+     * The organization that owns the audited model.
+     * The audits of the model are deleted (via foreign key cascade) when the organization is deleted.
+     */
+    public function getAuditOwnerOrganizationId(): ?string
+    {
+        return $this->getAttributes()['organization_id'] ?? null;
+    }
+
+    /**
+     * The user that owns the audited model.
+     * The audits of the model are deleted (via foreign key cascade) when the user is deleted.
+     */
+    public function getAuditOwnerUserId(): ?string
+    {
+        return null;
+    }
+
+    /**
+     * Models that are the owner of their own audits can not record the deletion audit,
+     * since the audit would reference the already deleted model and therefore violate the foreign key.
+     */
+    protected function isAuditOwnerOfItself(): bool
+    {
+        return false;
+    }
+
+    /**
+     * @return array<int|string, string>
+     */
+    public function getAuditEvents(): array
+    {
+        $events = $this->auditEvents ?? Config::get('audit.events', [
+            'created',
+            'updated',
+            'deleted',
+            'restored',
+        ]);
+
+        if ($this->isAuditOwnerOfItself()) {
+            $events = array_filter($events, fn (string $value, int|string $key): bool => (is_int($key) ? $value : $key) !== 'deleted', ARRAY_FILTER_USE_BOTH);
+        }
+
+        return $events;
+    }
+
+    /**
+     * @param  array<string, mixed>  $data
+     * @return array<string, mixed>
+     */
+    public function transformAudit(array $data): array
+    {
+        $data['owner_organization_id'] = $this->getAuditOwnerOrganizationId();
+        $data['owner_user_id'] = $this->getAuditOwnerUserId();
+
+        return $data;
+    }
 }