fix : 테이블 추가 및 수정

- 신규 (user_roles, user_tenants)
- 수정 (roles, tenants, users)

app/Models/UserTenant.php

@@ -0,0 +1,25 @@
+<?php
+
+namespace App\Models;
+
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\SoftDeletes;
+
+class UserTenant extends Model
+{
+    use SoftDeletes;
+
+    protected $fillable = [
+        'user_id', 'tenant_id', 'is_active', 'joined_at', 'left_at'
+    ];
+
+    public function user()
+    {
+        return $this->belongsTo(User::class);
+    }
+
+    public function tenant()
+    {
+        return $this->belongsTo(Tenant::class);
+    }
+}