ttrss: Add management of postgresql daemon in a shared manner

- This allows ttrss to disabled postgresql if it is not needed by any other app
and enable postgresql if it is disabled and ttrss is being enabled.

Tests:

- When disabling ttrss and it is the last app using postgresql, it will be
disabled too.

- When disabling ttrss and it is not the last app using postgresql, it will not
be disabled too.

- When enabling ttrss if postgresql is disabled, it will be enabled too.

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

plinth/modules/ttrss/__init__.py

@@ -7,7 +7,7 @@ from django.utils.translation import gettext_lazy as _
 from plinth import app as app_module
 from plinth import cfg, frontpage, menu
 from plinth.config import DropinConfigs
-from plinth.daemon import Daemon
+from plinth.daemon import Daemon, SharedDaemon
 from plinth.modules.apache.components import Webserver
 from plinth.modules.backups.components import BackupRestore
 from plinth.modules.firewall.components import Firewall
@@ -85,8 +85,11 @@ class TTRSSApp(app_module.App):
                               last_updated_version=5)
         self.add(webserver)
 
-        daemon = Daemon('daemon-ttrss', 'tt-rss')
-        self.add(daemon)
+        daemon1 = SharedDaemon('shared-daemon-ttrss-postgresql', 'postgresql')
+        self.add(daemon1)
+
+        daemon2 = Daemon('daemon-ttrss', 'tt-rss')
+        self.add(daemon2)
 
         users_and_groups = UsersAndGroups('users-and-groups-ttrss',
                                           groups=groups)
@@ -98,6 +101,7 @@ class TTRSSApp(app_module.App):
 
     def enable(self):
         """Enable components and API access."""
+        super().enable()
         privileged.enable_api_access()
 
         # Try to set the domain to one of the available TLS domains
@@ -107,8 +111,6 @@ class TTRSSApp(app_module.App):
             domain = next(names.get_available_tls_domains(), None)
             privileged.set_domain(domain)
 
-        super().enable()
-
     def setup(self, old_version):
         """Install and configure the app."""
         privileged.pre_setup()