letsencrypt: Use AppView for app page

Tests:

- Enable/disable button is not shown.

- List of certificates in the system is shown.

- Diagnostics menu item is shown and works.

- Certificate operations work.

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

plinth/modules/letsencrypt/__init__.py

@@ -50,6 +50,8 @@ class LetsEncryptApp(app_module.App):
 
     _version = 3
 
+    can_be_disabled = False
+
     def __init__(self):
         """Create components for the app."""
         super().__init__()

plinth/modules/letsencrypt/urls.py

@@ -8,7 +8,8 @@ from django.urls import re_path
 from . import views
 
 urlpatterns = [
-    re_path(r'^sys/letsencrypt/$', views.index, name='index'),
+    re_path(r'^sys/letsencrypt/$', views.LetsEncryptAppView.as_view(),
+            name='index'),
     re_path(r'^sys/letsencrypt/obtain/(?P<domain>[^/]+)/$', views.obtain,
             name='obtain'),
     re_path(r'^sys/letsencrypt/re-obtain/(?P<domain>[^/]+)/$', views.reobtain,

plinth/modules/letsencrypt/views.py

@@ -7,30 +7,28 @@ import logging
 
 from django.contrib import messages
 from django.shortcuts import redirect
-from django.template.response import TemplateResponse
 from django.urls import reverse_lazy
 from django.utils.translation import gettext as _
 from django.views.decorators.http import require_POST
 
-from plinth import app as app_module
 from plinth.errors import ActionError
 from plinth.modules import letsencrypt
+from plinth.views import AppView
 
 logger = logging.getLogger(__name__)
 
 
-def index(request):
-    """Serve configuration page."""
-    status = letsencrypt.get_status()
-    app = app_module.App.get('letsencrypt')
-    return TemplateResponse(
-        request, 'letsencrypt.html', {
-            'app_id': 'letsencrypt',
-            'app_info': app.info,
-            'status': status,
-            'has_diagnostics': True,
-            'is_enabled': app.is_enabled(),
-        })
+class LetsEncryptAppView(AppView):
+    """Show Let's Encrypt app main page."""
+
+    app_id = 'letsencrypt'
+    template_name = 'letsencrypt.html'
+
+    def get_context_data(self, *args, **kwargs):
+        """Add additional context data for template."""
+        context = super().get_context_data(*args, **kwargs)
+        context['status'] = letsencrypt.get_status()
+        return context
 
 
 @require_POST