title: In Django REST control serializer does not automatically remove spaces？
body: <p>model.py  </p>
  
  <pre><code>class Msg(models.Model):
      content = models.CharField(max_length=1024, null=True)
  </code></pre>
  
  <p>serializer.py</p>
  
  <pre><code>class MessageSerializer(serializers.ModelSerializer):
      class Meta:
          model = Msg
          fields = ["content"]
  </code></pre>
  
  <p>have data：</p>
  
  <pre><code>{"content": "   space    test    "}
  </code></pre>
  
  <p>and </p>
  
  <pre><code>print(data)
  serializer = MessageSerializer(data=data)
  if serializer.is_valid():
      serializer.save()
      print(serializer.data)
      return True, serializer.data
  else:
      return False, serializer.errors
  </code></pre>
  
  <p>first print is 
  <code>{'content': '      space      test           '}
  </code>
  second print is 
  <code>{'content': 'space      test'}
  </code>
  So the spaces in the database disappeared.<br>
  How do I keep spaces?</p>