move from real users to passwd file

mail-server/common.nix

@@ -14,10 +14,14 @@
 #  You should have received a copy of the GNU General Public License
 #  along with this program. If not, see <http://www.gnu.org/licenses/>
 
-{ config }:
+{ config, lib }:
 
 let
   cfg = config.mailserver;
+  # passwd :: [ String ]
+  passwd = lib.mapAttrsToList
+    (name: value: "${name}:${value.hashedPassword}:${builtins.toString cfg.vmailUID}:${builtins.toString cfg.vmailUID}::${cfg.mailDirectory}:/run/current-system/sw/bin/nologin:")
+            cfg.loginAccounts;
 in
 {
   # cert :: PATH
@@ -37,4 +41,6 @@ in
               else if cfg.certificateScheme == 3
                    then "/var/lib/acme/${cfg.fqdn}/key.pem"
                    else throw "Error: Certificate Scheme must be in { 1, 2, 3 }";
+  # passwdFile :: PATH
+  passwdFile = builtins.toFile "passwd" (lib.concatStringsSep "\n" passwd);
 }