i2p: Use drop-in config component for /etc files

Tests:

- Could not test as the app is uninstallable

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

debian/freedombox.maintscript

@@ -108,3 +108,4 @@ rm_conffile /etc/postfix/freedombox-aliases.cf 23.10~
 rm_conffile /etc/gitweb-freedombox.conf 23.10~
 rm_conffile /etc/apache2/conf-available/gitweb-freedombox.conf 23.10~
 rm_conffile /etc/apache2/conf-available/gitweb-freedombox-auth.conf 23.10~
+rm_conffile /etc/apache2/conf-available/i2p-freedombox.conf 23.10~

plinth/modules/i2p/__init__.py

@@ -5,6 +5,7 @@ from django.utils.translation import gettext_lazy as _
 
 from plinth import app as app_module
 from plinth import frontpage, menu
+from plinth.config import DropinConfigs
 from plinth.daemon import Daemon
 from plinth.modules.apache.components import Webserver
 from plinth.modules.backups.components import BackupRestore
@@ -39,7 +40,7 @@ class I2PApp(app_module.App):
 
     app_id = 'i2p'
 
-    _version = 2
+    _version = 3
 
     def __init__(self):
         """Create components for the app."""
@@ -70,6 +71,11 @@ class I2PApp(app_module.App):
         packages = Packages('packages-i2p', ['i2p'])
         self.add(packages)
 
+        dropin_configs = DropinConfigs('dropin-configs-i2p', [
+            '/etc/apache2/conf-available/i2p-freedombox.conf',
+        ])
+        self.add(dropin_configs)
+
         firewall = Firewall('firewall-i2p-web', info.name,
                             ports=['http', 'https'], is_external=True)
         self.add(firewall)