title: Django Channels setting custom channel_name
body: <p>I'm using Django channels and I'm able to properly connect and send message with builtin channel_name provided.
  I'm wondering if there is a way to change and register a custom channel_name within web socket connection. 
  I tried changing it but channel_layer alredy stored builtin channel_name and I'm unable to send a message.</p>
  
  <p>This is a provided test class</p>
  
  <pre class="lang-py prettyprint-override"><code>class TestWebSocket(AsyncWebsocketConsumer): 
     async def connect(self):
          self.channel_name = "custom.channelname.UNIQUE"
          await self.accept()
  
     async def test_message(self, event):
          await self.send(text_data=json.dumps({
              'message': event['message']
          }))
  </code></pre>
  
  <p>Here how I send a message:</p>
  
  <pre class="lang-py prettyprint-override"><code>async_to_sync(channel_layer.send)('custom.channelname.UNIQUE',
                                    {'type': 'test.message', 'message': 'dfdsdsf'})
  </code></pre>
  
  <p>I read documentation and it stores <code>channel_name</code> inside <em>db</em>, but each time I perform a connection, that name will change. I want to avoid flooding <em>db</em> with update calls.
  So this is why I'm trying to force my own channel names. </p>
  
  <p>There is a way to change it or is oly waste of time?</p>