title: rails_admin belongs_to field selection rename
body: <p>I have the following model available in my app.</p>
  
  <pre><code>class Category &lt; ActiveRecord::Base
    validates :name, :presence =&gt; true
    validates :name, :uniqueness =&gt; { :scope =&gt; :parent_id, :case_sensitive =&gt; false }
  
    belongs_to :parent, :class_name =&gt; "Category"
    has_many :children, :class_name =&gt; "Category", :foreign_key =&gt; "parent_id"
  end
  </code></pre>
  
  <p>And I also have rails_admin enabled in my app. In the auto-generated admin site, I am having problem with selecting the parent and children category as shown in the image attached.</p>
  
  <p><img src="https://i.stack.imgur.com/wuwzu.png" alt="Rails Admin sample"></p>
  
  <p>In this example, I actually have "Desktop Memory" (child) under "Memory" (parent). How do I identify it in the dropdown menu and also the selection list? Perhaps with something like "Memory - Desktop Memory".</p>