perf: 支持slack通知和认证 (#12193)

* perf: 支持slack通知和认证

* perf: 生成迁移文件

* perf: 优化获取access_token逻辑

---------

Co-authored-by: jiangweidong <weidong.jiang@fit2cloud.com>

apps/notifications/backends/slack.py

@@ -0,0 +1,21 @@
+from django.conf import settings
+
+from common.sdk.im.slack import Slack as Client
+from .base import BackendBase
+
+
+class Slack(BackendBase):
+    account_field = 'slack_id'
+    is_enable_field_in_settings = 'AUTH_SLACK'
+
+    def __init__(self):
+        self.client = Client(
+            bot_token=settings.SLACK_BOT_TOKEN,
+        )
+
+    def send_msg(self, users, message, subject=None):
+        accounts, __, __ = self.get_accounts(users)
+        return self.client.send_text(accounts, message)
+
+
+backend = Slack