flip host and user

nix/flakeModule.nix

@@ -68,7 +68,7 @@ in
         )
       );
 
-      # Every user on every host is a home identity "<hostName>@<userName>".
+      # Every user on every host is a home identity "<userName>@<hostName>".
       home_keys = lib.mergeAttrsList (
         lib.flatten (
           map (
@@ -76,7 +76,7 @@ in
             lib.mapAttrsToList (
               _: host:
               lib.mapAttrsToList (
-                _: user: { "${host.hostName}@${user.userName}" = toKeyList (user.sopsPublic or [ ]); }
+                _: user: { "${user.userName}@${host.hostName}" = toKeyList (user.sopsPublic or [ ]); }
               ) (host.users or { })
             ) perSystem
           ) (builtins.attrValues den.hosts)