Add initial Code

app/Models/LineItem.php

@@ -0,0 +1,26 @@
+<?php
+
+namespace App\Models;
+
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Factories\HasFactory;
+
+class LineItem extends Model
+{
+    use HasFactory;
+
+    protected $fillable = [
+        'invoice_id',
+        'position',
+        'title',
+        'description',
+        'quantity',
+        'unit',
+        'price',
+    ];
+
+    public function invoice()
+    {
+        return $this->belongsTo(Invoice::class);
+    }
+}