add default needed for one way backup contracts

modules/blocks/postgresql.nix

@@ -55,6 +55,7 @@ in
         Backup configuration.
       '';
 
+      default = {};
       type = lib.types.submodule {
         options = contracts.databasebackup.mkRequester {
           user = "postgres";
@@ -169,10 +170,5 @@ in
             (upgrade-script 15 16)
           ];
         }
-        {
-          # Seems superfluous but otherwise we get:
-          # The option `shb.postgresql.databasebackup' was accessed but has no value defined.
-          shb.postgresql.databasebackup = {};
-        }
       ]);
 }

modules/services/forgejo.nix

@@ -244,6 +244,7 @@ in
       description = ''
         Backup configuration.
       '';
+      default = {};
       type = lib.types.submodule {
         options = contracts.backup.mkRequester {
           user = options.services.forgejo.user.value;

modules/services/home-assistant.nix

@@ -143,6 +143,7 @@ in
       description = ''
         Backup configuration.
       '';
+      default = {};
       type = lib.types.submodule {
         options = contracts.backup.mkRequester {
           user = "hass";

modules/services/jellyfin.nix

@@ -154,6 +154,7 @@ in
       description = ''
         Backup configuration.
       '';
+      default = {};
       type = lib.types.submodule {
         options = contracts.backup.mkRequester {
           user = "jellyfin";

modules/services/nextcloud-server.nix

@@ -522,6 +522,7 @@ in
       description = ''
         Backup configuration.
       '';
+      default = {};
       type = lib.types.submodule {
         options = contracts.backup.mkRequester {
           user = "nextcloud";

modules/services/vaultwarden.nix

@@ -131,6 +131,7 @@ in
       description = ''
         Backup configuration.
       '';
+      default = {};
       type = lib.types.submodule {
         options = contracts.backup.mkRequester {
           user = "vaultwarden";
@@ -231,9 +232,5 @@ in
     # TODO: make this work.
     # It does not work because it leads to infinite recursion.
     # ${cfg.mount}.path = dataFolder;
-
-    # Seems superfluous but otherwise we get:
-    # The option `shb.vaultwarden.backup' was accessed but has no value defined.
-    shb.vaultwarden.backup = {};
   };
 }