title: How to accept a list query parameter with standard format in DRF using django_filters
body: <p>I want to be able to accept a list query param using the standard <code>application/x-www-form-urlencoded</code> format, as stated in <a href="https://stackoverflow.com/a/9176496/4650346">https://stackoverflow.com/a/9176496/4650346</a>. For example to filter products by a list of categories, I would like to use:</p>
  
  <pre><code>http://my.api.com/products?category[]=shirts&amp;category[]=sweaters
  </code></pre>
  
  <p>I can create a FilterSet that acomplish this multiple choice filtering, the issue is that it won't follow the standard as I am unable to add the suffix <code>[]</code> that express it is a list. The following class demonstrates the functionality that I need.</p>
  
  <pre class="lang-py prettyprint-override"><code>class MyFilter(django_filters.FilterSet):
      category = django_filters.ModelMultipleChoiceFilter(
          queryset=Category.objects.all(), 
          name='categories'
      )
      class Meta:
          model = MyModel
          fields = ['category',]
  </code></pre>
  
  <p>That code, will allow users to create requests as:</p>
  
  <pre><code>http://my.api.com/products?category=shirt&amp;category=sweaters
  </code></pre>
  
  <p>Question is: how can I add the suffix <code>[]</code> to the GET parameters that represent a list in the URI?</p>
  
  <p>Cheers,</p>