add backup script, akina to moria via crimespoon

requires a ssh key authorized to postgres@akina on crimespoon

hosts/crimespoon/configuration.nix

@@ -68,6 +68,32 @@
     timerConfig.OnCalendar="*-*-* 2:00:00";
   };
 
+  # Enable backing up Akina Postgres DB to Akina via rsync
+  systemd.services.akina_rsync_backup = {
+    serviceConfig.Type = "oneshot";
+    path = with pkgs; [ openssh rsync coreutils ];
+    script = ''
+      set -e
+      BACKUP_FILENAME=pg_dumpall-$(hostname)-$(date --iso-8601).sql.gz 
+
+      ssh postgres@nora.codes -i ~/.ssh/crimespoon-akina-backup-key "pg_dumpall --clean | gzip > $BACKUP_FILENAME"
+
+      scp -i ~/.ssh/crimespoon-akina-backup-key postgres@nora.codes:$BACKUP_FILENAME ./$BACKUP_FILENAME
+
+      ssh postgres@nora.codes -i ~/.ssh/crimespoon-akina-backup-key "rm $BACKUP_FILENAME"
+
+      rsync -a --delete $BACKUP_FILENAME moria.local::CRIMESPOON/akina/$BACKUP_FILENAME
+
+      rm $BACKUP_FILENAME
+    '';
+  };
+
+  systemd.timers.akina_rsync_backup = {
+    wantedBy = [ "timers.target" ];
+    partOf = [ "akina_rsync_backup.service" ];
+    timerConfig.OnCalendar="Weekly";
+  };
+
   services.openssh.enable = true;
   system.stateVersion = "21.11"; # Did you read the comment?
 }