deluge: Completely uninstall app

Remove deluge default file, config directory, and systemd service file

Test:
1. In a Vagrant box manually install the app
2. Modify the default download path and change the default password
3. Uninstall the app
4. Confirm that the download path and password are reset to default
5. Also test enabling and disabling the app after reinstallation

Signed-off-by: nbenedek <contact@nbenedek.me>
[sunil: Update docstings and make uninstall fail-safe]
Signed-off-by: Sunil Mohan Adapa <sunil@medhas.org>
Reviewed-by: Sunil Mohan Adapa <sunil@medhas.org>

plinth/modules/deluge/__init__.py

@@ -100,3 +100,8 @@ class DelugeApp(app_module.App):
         add_user_to_share_group(SYSTEM_USER)
         privileged.setup()
         self.enable()
+
+    def uninstall(self):
+        """De-configure and uninstall the app."""
+        super().uninstall()
+        privileged.uninstall()

plinth/modules/deluge/privileged.py

@@ -2,6 +2,7 @@
 """Configuration helper for BitTorrent web client."""
 
 import pathlib
+import shutil
 import subprocess
 import time
 
@@ -154,3 +155,12 @@ def _wait_for_configuration(service, file_name):
 
     if not is_running:
         action_utils.service_stop(service)
+
+
+@privileged
+def uninstall():
+    """Remove configuration and service files."""
+    for item in DELUGED_DEFAULT_FILE, DELUGE_WEB_SYSTEMD_SERVICE_PATH:
+        pathlib.Path(item).unlink(missing_ok=True)
+
+    shutil.rmtree(DELUGE_CONF_DIR, ignore_errors=True)