Currently `SlackWebhookHook` gets the token from `extra` but it would be more secure and intuitive to have it in password.

https://github.com/apache/airflow/blob/4fb5c017fe5ca41ed95547a857c9c39efc4f1476/airflow/providers/slack/hooks/slack_webhook.py
tests/providers/slack/hooks/test_slack_webhook.py
conn_id = 'slack-webhook-default'
        hook = SlackWebhookHook(http_conn_id=conn_id)
        expected_webhook_token = 'your_token_here'
        
        webhook_token = hook._get_token(None, conn_id)
        
        self.assertEqual(webhook_token, expected_webhook_token)
    def test_build_slack_message(self):
        
        hook = SlackWebhookHook(**self._config)
        
        message = hook._build_slack_message()
        
        self.assertEqual(self.expected_message_dict, json.loads(message))
    @mock.patch('requests.Session')
    @mock.patch('requests.Request')
    def test_url_generated_by_http_conn_id(self, mock_request, mock_session):
        hook = SlackWebhookHook(http_conn_id='slack-webhook-url')
        try:
            hook.execute()
        except MissingSchema:
            pass
        mock_request.assert_called_once_with(
            self.expected_method, self.expected_url, headers=mock.ANY, data=mock.ANY
        )
        mock_request.reset_mock()
    @mock.patch('requests.Session')
    @mock.patch('requests.Request')
    def test_url_generated_by_endpoint(self, mock_request, mock_session):