title: Laravel hasOneThrough relationship returns null
body: <p>I have the following table structure in MySQL database:</p>
  <pre><code>Products
      id - integer
      name - string
      user_id -string
  
  Users
      user_id - string
      password - string
      person_id - integer
  
  Persons
      person_id - integer
      name - string
      email - integer
  </code></pre>
  <p>I am using <code>hasOneThrough</code> relationship on Products model to get the details about the <code>Person</code>, who is linked through <code>Users</code>. The code that defines the relation is as follows :</p>
  <pre><code>public function product_user()
  {
      return $this-&gt;hasOneThrough(
          'App\Person',
          'App\User',
          'person_id',
          'person_id',
          'user_id',
          'user_id'
       );
  }
  </code></pre>
  <p>But I am getting <code>null</code> when I try to access the property <code>product_user</code>, it is giving me <code>null</code> all the time. I cannot change the database structure. How can I define a proper relationship in this scenario ?</p>