Fix Mastodon from being wiped

modules/system/services/server/mastodon/default.nix

@@ -5,6 +5,8 @@
       localDomain = "social.${config.vars.primeDomain}";
       streamingProcesses = 4;
       configureNginx = true;
+
+      # Set up email security
       smtp = {
         createLocally = false;
         host = "mx.${config.vars.mailDomain}";
@@ -15,6 +17,9 @@
         passwordFile = pkgs.writeText "smtp_pass.txt" config.secrets.mailPass.nixfoxNoReply;
       };
     };
-    environment.persistence."/persist".directories = [ "/var/lib/mastodon" ];
+    environment.persistence."/persist".directories = [
+      "/var/lib/mastodon"
+      "/var/lib/postgresql"
+    ];
   };
 }