add element persistence

backend/app/Element/ElementModel.php

@@ -0,0 +1,47 @@
+<?php
+
+namespace App\Element;
+
+use Illuminate\Database\Eloquent\Attributes\Fillable;
+use Illuminate\Database\Eloquent\Builder;
+use Illuminate\Database\Eloquent\Model;
+
+/**
+ * @property int $id
+ * @property int $set_id
+ * @property string $name
+ * @property string $kind
+ * @property int|null $parent_element_id
+ * @property int $position
+ *
+ * @method static Builder<static>|ElementModel newModelQuery()
+ * @method static Builder<static>|ElementModel newQuery()
+ * @method static Builder<static>|ElementModel query()
+ *
+ * @mixin \Eloquent
+ */
+#[Fillable([
+    'set_id',
+    'name',
+    'kind',
+    'parent_element_id',
+    'position',
+])]
+class ElementModel extends Model
+{
+    protected $table = 'elements';
+
+    public $timestamps = false;
+
+    /**
+     * @return array<string, string>
+     */
+    protected function casts(): array
+    {
+        return [
+            'set_id' => 'integer',
+            'parent_element_id' => 'integer',
+            'position' => 'integer',
+        ];
+    }
+}