title: Object of type datetime is not JSON serializable error
body: <p>I have some issues with using a DateTime value in python. When I use session_start in the following code, I get an Object of type datetime is not JSON serializable error</p>
  
  <p>views.py</p>
  
  <pre><code>    dataSourceBar = {}
      dataSourceBar['chart'] = {
          "caption": "Rainfall",
              "subCaption": "Shown per date",
              "xAxisName": "Session",
              "yAxisName": "Rainfall in MM",
              "theme": "candy"
          }
  
      dataSourceBar['data'] = []  
  
      objects_with_category_id_2 = dashboard_input.objects.filter(category_category_id=2)
  
      for obj in objects_with_category_id_2:
          data =  {'label': obj.session_start,
                   'value': obj.input_input_value}
          dataSourceBar['data'].append(data)  
  </code></pre>
  
  <p>model.py</p>
  
  <pre><code>class dashboard_input(models.Model):
      session_start = models.DateTimeField(max_length=100)
  </code></pre>
  
  <p>traceback</p>
  
  <pre><code>Internal Server Error: /dashboard/
  Traceback (most recent call last):
    File "C:\Users\natas\AppData\Local\Programs\Python\Python37-32\lib\site-packages\django\core\handlers\exception.py", line 34, in inner
      response = get_response(request)
    File "C:\Users\natas\AppData\Local\Programs\Python\Python37-32\lib\site-packages\django\core\handlers\base.py", line 126, in _get_response
      response = self.process_exception_by_middleware(e, request)
    File "C:\Users\natas\AppData\Local\Programs\Python\Python37-32\lib\site-packages\django\core\handlers\base.py", line 124, in _get_response
      response = wrapped_callback(request, *callback_args, **callback_kwargs)
    File "C:\var\www\VSDK\vsdk\dashboard\views.py", line 69, in Chart
      return  render(request, 'dash.html', {'output' : column2D.render(),'output2' : doughnut3d.render()})
    File "C:\var\www\VSDK\vsdk\dashboard\fusioncharts.py", line 52, in render
      self.readyJson = json.dumps(self.constructorOptions, ensure_ascii=False)
    File "C:\Users\natas\AppData\Local\Programs\Python\Python37-32\lib\json\__init__.py", line 238, in dumps
      **kw).encode(obj)
    File "C:\Users\natas\AppData\Local\Programs\Python\Python37-32\lib\json\encoder.py", line 199, in encode
      chunks = self.iterencode(o, _one_shot=True)
    File "C:\Users\natas\AppData\Local\Programs\Python\Python37-32\lib\json\encoder.py", line 257, in iterencode
      return _iterencode(o, 0)
    File "C:\Users\natas\AppData\Local\Programs\Python\Python37-32\lib\json\encoder.py", line 179, in default
      raise TypeError(f'Object of type {o.__class__.__name__} '
  TypeError: Object of type datetime is not JSON serializable
  </code></pre>
  
  <p>I retrieve the value from a database view which is filled by other tables where the user fills in their data.</p>
  
  <p>Could someone help me with this?</p>