feat: Implement refresh token system for client authentication, including token creation, rotation, and revocation.

app/Models/RefreshToken.php

@@ -0,0 +1,28 @@
+<?php
+
+namespace App\Models;
+
+use Illuminate\Database\Eloquent\Model;
+
+class RefreshToken extends Model
+{
+    protected $fillable = [
+        'customer_id',
+        'token',
+        'expires_at',
+    ];
+
+    protected $casts = [
+        'expires_at' => 'datetime',
+    ];
+
+    public function customer()
+    {
+        return $this->belongsTo(Customer::class);
+    }
+
+    public function isExpired(): bool
+    {
+        return $this->expires_at->isPast();
+    }
+}