privoxy: Enable backup/restore (no data)

Reviewed-by: James Valleroy <jvalleroy@mailbox.org>

functional_tests/features/privoxy.feature

@@ -15,7 +15,7 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #
 
-@apps @privoxy
+@apps @privoxy @backups
 Feature: Privoxy Web Proxy
   Proxy web connections for enhanced privacy.
 
@@ -32,3 +32,10 @@ Scenario: Disable privoxy application
   Given the privoxy application is enabled
   When I disable the privoxy application
   Then the privoxy service should not be running
+
+Scenario: Backup and restore privoxy
+  Given the privoxy application is enabled
+  When I create a backup of the privoxy app data
+  And I export the privoxy app data backup
+  And I restore the privoxy app data backup
+  Then the privoxy service should be running

plinth/modules/privoxy/__init__.py

@@ -27,6 +27,8 @@ from plinth.menu import main_menu
 from plinth.utils import format_lazy
 from plinth.views import ServiceView
 
+from .manifest import backup
+
 version = 1
 
 is_essential = False

plinth/modules/privoxy/manifest.py

@@ -0,0 +1,23 @@
+#
+# This file is part of FreedomBox.
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as
+# published by the Free Software Foundation, either version 3 of the
+# License, or (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+"""
+Application manifest for privoxy.
+"""
+
+from plinth.modules.backups.api import validate as validate_backup
+
+backup = validate_backup({})