wordpress: Completely uninstall app

* When app is uninstalled, remove config files and drop the database
* Declare PUBLIC_ACCESS_FILE with pathlib.Path
* Add public access file to the backup manifest

Tests:
1. Install and setup wordpress
2. Reinstall the app and confirm that the initial setup page is shown to the user
3. Functional tests passed

Signed-off-by: nbenedek <contact@nbenedek.me>
[sunil: Update docstrings, minor refactoring]
Signed-off-by: Sunil Mohan Adapa <sunil@medhas.org>
Reviewed-by: Sunil Mohan Adapa <sunil@medhas.org>

plinth/modules/wordpress/__init__.py

@@ -111,6 +111,11 @@ class WordPressApp(app_module.App):
             # Apply changes to Apache configuration from v2 to v3.
             service_privileged.reload('apache2')
 
+    def uninstall(self):
+        """De-configure and uninstall the app."""
+        super().uninstall()
+        privileged.uninstall()
+
 
 class WordPressBackupRestore(BackupRestore):
     """Component to backup/restore WordPress."""

plinth/modules/wordpress/manifest.py

@@ -12,7 +12,8 @@ clients = [{
 
 backup = {
     'data': {
-        'files': ['/var/lib/plinth/backups-data/wordpress-database.sql'],
+        'files': ['/var/lib/plinth/backups-data/wordpress-database.sql',
+                  '/etc/wordpress/is_public'],
         'directories': ['/var/lib/wordpress/']
     },
     'secrets': {

plinth/modules/wordpress/privileged.py

@@ -13,8 +13,7 @@ import augeas
 from plinth import action_utils
 from plinth.actions import privileged
 
-PUBLIC_ACCESS_FILE = '/etc/wordpress/is_public'
+_public_access_file = pathlib.Path('/etc/wordpress/is_public')
-
 _config_file_path = pathlib.Path('/etc/wordpress/config-default.php')
 _static_config_file_path = pathlib.Path('/etc/wordpress/freedombox-static.php')
 _db_file_path = pathlib.Path('/etc/wordpress/database.php')
@@ -127,18 +126,17 @@ def _upgrade_config_file():
 @privileged
 def set_public(enable: bool):
     """Allow/disallow public access."""
-    public_access_file = pathlib.Path(PUBLIC_ACCESS_FILE)
     if enable:
-        public_access_file.touch()
+        _public_access_file.touch()
     else:
-        public_access_file.unlink(missing_ok=True)
+        _public_access_file.unlink(missing_ok=True)
 
     action_utils.service_reload('apache2')
 
 
 def is_public() -> bool:
     """Return whether public access is enabled."""
-    return pathlib.Path(PUBLIC_ACCESS_FILE).exists()
+    return _public_access_file.exists()
 
 
 @privileged
@@ -177,3 +175,18 @@ def _load_augeas():
     aug.load()
 
     return aug
+
+
+@privileged
+def uninstall():
+    """Remove config files and drop database."""
+    _drop_database()
+    for file_ in [_public_access_file, _config_file_path, _db_file_path]:
+        file_.unlink(missing_ok=True)
+
+
+def _drop_database():
+    """Drop the mysql database that was created during install."""
+    query = f'''DROP DATABASE {DB_NAME};'''
+    subprocess.run(['mysql', '--user', 'root'], input=query.encode(),
+                   check=True)