Replace redis with keydb

Due to Redis licensing not being opensource anymore, here's a drop-in replacement with an opensource license.

Source:
https://redis.com/blog/redis-adopts-dual-source-available-licensing/
https://github.com/Snapchat/KeyDB/blob/main/COPYING

docker-compose.yml

@@ -12,7 +12,7 @@ services:
       - "SMARTHOST_ALIASES=${SMARTHOST_ALIASES}"
 
   redis:
-    image: redis:7.2
+    image: eqalpha/keydb:x86_64_v6.3.4
 
   db:
     # We use MariaDB because it supports ARM and has the expected collations