letsencrypt: Use drop-in config component for /etc files

Tests:

- Config files are all symlinks in /etc/
- Unable to test renewal hook

Signed-off-by: Sunil Mohan Adapa <sunil@medhas.org>
Reviewed-by: James Valleroy <jvalleroy@mailbox.org>

debian/freedombox.maintscript

@@ -113,3 +113,4 @@ rm_conffile /etc/ikiwiki/plinth-blog.setup 23.10~
 rm_conffile /etc/ikiwiki/plinth-wiki.setup 23.10~
 rm_conffile /etc/apache2/conf-available/ikiwiki-plinth.conf 23.10~
 rm_conffile /etc/apache2/conf-available/janus-freedombox.conf 23.10~
+rm_conffile /etc/letsencrypt/renewal-hooks/deploy/50-freedombox 23.10~

plinth/modules/letsencrypt/__init__.py

@@ -9,6 +9,7 @@ from django.utils.translation import gettext_lazy as _
 
 from plinth import app as app_module
 from plinth import cfg, menu
+from plinth.config import DropinConfigs
 from plinth.modules import names
 from plinth.modules.apache.components import diagnose_url
 from plinth.modules.backups.components import BackupRestore
@@ -44,7 +45,7 @@ class LetsEncryptApp(app_module.App):
 
     app_id = 'letsencrypt'
 
-    _version = 3
+    _version = 4
 
     can_be_disabled = False
 
@@ -69,6 +70,11 @@ class LetsEncryptApp(app_module.App):
         packages = Packages('packages-letsencrypt', ['certbot'])
         self.add(packages)
 
+        dropin_configs = DropinConfigs('dropin-configs-letsencrypt', [
+            '/etc/letsencrypt/renewal-hooks/deploy/50-freedombox',
+        ])
+        self.add(dropin_configs)
+
         backup_restore = BackupRestore('backup-restore-letsencrypt',
                                        **manifest.backup)
         self.add(backup_restore)