title: Force django admin search bar to be case insensitive
body: <p>My problem is that for one of my models, the search bar from the corresponding admin page is performing a case <strong>sensitive</strong> search when it should be a case <strong>insensitive</strong> search by default.</p>
  
  <p>From what I could find <a href="https://groups.google.com/forum/#!topic/django-users/dLy6-FT4Yjs" rel="nofollow noreferrer">here</a>, I feel like this might have something to do with database encoding but from <a href="https://docs.djangoproject.com/en/2.1/ref/unicode/" rel="nofollow noreferrer">the doc</a>, it says that Django assumes that everything is UTF-8 encoded and I checked my MySQL table and the fields are encoded in UTF-8.</p>
  
  <p>Could it be due to the presence of Greek characters in one of my field? How can I force a case insensitive search in <strong>at least</strong> the fields that don't contain Greek letters? Currently, the search is case sensitive for all the fields. But it works correctly (case insensitive) for other models.</p>
  
  <p>Model:</p>
  
  <pre><code>class MyModel(models.Model):
      id = models.AutoField(primary_key=True)
      field1 = models.CharField(max_length=200) # Might contain greek letters
      field2 = models.CharField(max_length=200, unique=True)
  </code></pre>
  
  <p>Not sharing the admin class  code as nothing fancy is in here. Just standard combination of <code>list_display</code>, <code>search_fields</code>, <code>ordering</code> and <code>fieldsets</code>.</p>
  
  <p>Using Django 1.10</p>
  
  <p><strong>EDIT</strong><br>
  Here is the output of <code>SHOW CREATE TABLE</code> for the table in question:</p>
  
  <pre><code>CREATE TABLE `my_model` (
      `id` int(11) NOT NULL AUTO_INCREMENT,
      `field1` varchar(200) COLLATE utf8_bin NOT NULL,
      `field2` varchar(200) COLLATE utf8_bin NOT NULL,
      # Non relevant other fields
      PRIMARY KEY (`id`),
      UNIQUE KEY `my_model_field2_63f9df5e_uniq` (`field2`)
  ) ENGINE=InnoDB AUTO_INCREMENT=657 DEFAULT CHARSET=utf8 COLLATE=utf8_bin
  </code></pre>
  
  <p>Now that I see that, it's probably due to <code>_bin</code> right? Should I convert to something with <code>_ci</code>? What's the way of doing that in Django?</p>