Add audit owner through parent model

Models that belong to an organization via a parent model (for example
project members via their project) implement AuditableThroughParent and
return the parent relation. The owner organization of their audits is
taken from the loaded parent if it matches the foreign key, otherwise it
is queried. The declaration is also used to backfill the owner of
existing audits.

app/Models/Concerns/AuditableThroughParent.php

@@ -0,0 +1,22 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Models\Concerns;
+
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Relations\BelongsTo;
+
+/**
+ * Marks an auditable model whose audits are owned by the owner of its parent model,
+ * because the model itself has no organization_id (for example a project member belongs to an organization via its project).
+ * The parent model has to have an organization_id column.
+ * This is used to set the owner of new audits (CustomAuditable) and to backfill the owner of existing audits.
+ */
+interface AuditableThroughParent
+{
+    /**
+     * @return BelongsTo<covariant Model, covariant Model>
+     */
+    public function getAuditParentRelation(): BelongsTo;
+}

app/Models/Concerns/CustomAuditable.php

@@ -4,6 +4,7 @@ declare(strict_types=1);
 
 namespace App\Models\Concerns;
 
+use Illuminate\Database\Eloquent\Model;
 use Illuminate\Support\Facades\Config;
 use OwenIt\Auditing\Auditable;
 
@@ -27,6 +28,36 @@ trait CustomAuditable
      */
     public function getAuditOwnerOrganizationId(): ?string
     {
+        if ($this instanceof AuditableThroughParent) {
+            $relation = $this->getAuditParentRelation();
+            $parentId = $this->getAttributes()[$relation->getForeignKeyName()] ?? null;
+            if ($parentId === null) {
+                return null;
+            }
+
+            // Note: The loaded parent is only used if it still matches the foreign key and was loaded with the organization
+            $relationName = $relation->getRelationName();
+            if ($this->relationLoaded($relationName)) {
+                $parent = $this->getRelation($relationName);
+                if ($parent instanceof Model
+                    && $parent->getAttribute($relation->getOwnerKeyName()) === $parentId
+                    && array_key_exists('organization_id', $parent->getAttributes())) {
+                    /** @var string|null $organizationId */
+                    $organizationId = $parent->getAttributes()['organization_id'];
+
+                    return $organizationId;
+                }
+            }
+
+            /** @var string|null $organizationId */
+            $organizationId = $relation->getRelated()->newQuery()
+                ->toBase()
+                ->where($relation->getOwnerKeyName(), $parentId)
+                ->value('organization_id');
+
+            return $organizationId;
+        }
+
         return $this->getAttributes()['organization_id'] ?? null;
     }
 

app/Models/ProjectMember.php

@@ -4,6 +4,7 @@ declare(strict_types=1);
 
 namespace App\Models;
 
+use App\Models\Concerns\AuditableThroughParent;
 use App\Models\Concerns\CustomAuditable;
 use App\Models\Concerns\HasUuids;
 use Database\Factories\ProjectMemberFactory;
@@ -29,7 +30,7 @@ use OwenIt\Auditing\Contracts\Auditable as AuditableContract;
  * @method static Builder<ProjectMember> whereBelongsToOrganization(Organization $organization)
  * @method static ProjectMemberFactory factory()
  */
-class ProjectMember extends Model implements AuditableContract
+class ProjectMember extends Model implements AuditableContract, AuditableThroughParent
 {
     use CustomAuditable;
 
@@ -83,11 +84,11 @@ class ProjectMember extends Model implements AuditableContract
         });
     }
 
-    public function getAuditOwnerOrganizationId(): ?string
+    /**
+     * @return BelongsTo<Project, $this>
+     */
+    public function getAuditParentRelation(): BelongsTo
     {
-        /** @var string|null $organizationId */
-        $organizationId = Project::query()->whereKey($this->project_id)->value('organization_id');
-
-        return $organizationId;
+        return $this->project();
     }
 }