Merge branch '173.zram' into 'develop'

Enable zram on all AWS VMs

See merge request !504

morph/lib/issuer-aws.nix

@@ -42,4 +42,8 @@
   # Turn on automatic optimization of nix store
   # https://nixos.wiki/wiki/Storage_optimization
   nix.settings.auto-optimise-store = true;
+
+  # Most of the time, we have ample free & usable memory, but when upgrading
+  # software, we sometimes run out because of Nix.  This is supposed to help:
+  zramSwap.enable = true;
 }