Add autojoin feature

utils/database.py

@@ -0,0 +1,20 @@
+from aioredis import Redis
+from typing import Sequence
+
+
+class AutoJoin:
+    @staticmethod
+    async def get_channels(redis: Redis) -> Sequence[tuple]:
+        # return all channels
+        channels = await redis.hgetall(name="autojoin")
+        return {key: value.split("-") for key, value in channels.items()}
+
+    @staticmethod
+    async def update_channel(redis: Redis, guild_id, voicechannel_id, textchannel_id):
+        await redis.hset(
+            name="autojoin", key=guild_id, value=f"{voicechannel_id}-{textchannel_id}"
+        )
+
+    @staticmethod
+    async def del_channel(redis: Redis, guild_id):
+        await redis.hdel("autojoin", guild_id)