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
airflow/providers/slack/hooks/slack_webhook.py
"""
        Construct the Slack message. All relevant parameters are combined here to a valid
        Slack json message.
        :return: Slack message to send
        :rtype: str
        """
        cmd = {}
        if self.channel:
            cmd['channel'] = self.channel
        if self.username:
            cmd['username'] = self.username
        if self.icon_emoji:
            cmd['icon_emoji'] = self.icon_emoji
        if self.icon_url:
            cmd['icon_url'] = self.icon_url
        if self.link_names:
            cmd['link_names'] = 1
        if self.attachments:
            cmd['attachments'] = self.attachments
        if self.blocks:
            cmd['blocks'] = self.blocks
        cmd['text'] = self.message
        return json.dumps(cmd)
    def execute(self) -> None: