Create database backups

When running `abra app backup`/`abra app restore`, use `pg_dump -Fc`.

This is the backup strategy recommended by hometown, just abra-ified.
(e.g. Update Steps here: https://github.com/hometown-fork/hometown/releases/tag/v4.2.10%2Bhometown-1.1.1)

compose.yml

@@ -189,6 +189,14 @@ services:
       - POSTGRES_DB=${DB_NAME}
       - POSTGRES_PASSWORD_FILE=/run/secrets/db_password
       - POSTGRES_USER=${DB_USER}
+    deploy:
+      labels:
+        - "backupbot.backup=true"
+        - "backupbot.backup.pre-hook=sh -c \"mkdir -p /var/backup/hometown; /usr/local/bin/pg_dump -Fc -U ${DB_USER} ${DB_NAME} > /var/backup/hometown/backupbot.dump\""
+        - "backupbot.backup.path=/var/backup/hometown"
+        - "backupbot.backup.post-hook=rm -f /var/backup/hometown/backupbot.dump"
+        - "backupbot.restore.post-hook=sh -c \"/usr/local/bin/pg_restore -U ${DB_USER} -d ${DB_NAME} -1 /var/backup/hometown/backupbot.dump\""
+
 
   redis:
     image: redis:7.2-alpine