cache: replace memcache with redis.

Drop memcache. Use redis for all caching instead.

config/docker/compose.yml

@@ -10,11 +10,6 @@ services:
     image: redis:latest
     ports:
       - "6379:6379"
-  memcached:
-    image: memcached:alpine
-    ports:
-      - "11211:11211"
-    command: memcached
   archives:
     image: r888888888/archives
     command: sleep 1d
@@ -39,7 +34,6 @@ services:
       - RO_DATABASE_URL
       - DEBUG
       - ARCHIVE_DATABASE_URL
-      - DANBOORU_MEMCACHED_SERVERS
       - DANBOORU_AWS_SQS_ARCHIVE_URL
       - DANBOORU_PIXIV_LOGIN
       - DANBOORU_PIXIV_PASSWORD
@@ -65,6 +59,5 @@ services:
       - "3000:3000"
     depends_on:
       - db
-      - memcached
       - archives
-      - redis
+      - redis