bind: Add daemon alias for bind9 -> named

bind9 package version 1:9.16.1-2 in unstable renamed bind9.service to
named.service. The new service file contains Alias=bind9.service. Use this
support multiple versions of the package across Debian stable, testing and
unstable.

Closes: #1816.

Tests performed:

- Enable the service. 'service enable bind9' is called but fails with error
ignored. 'service enable named' is also called but succeeds. Running 'service
is-enable bind9' and 'service is-enabled named' return success. App page show
enabled, there are no errors on the page.

- When app is enabled, there is no message that service is not running.

- When diagnostics are run, it shows that bind9 service is running.

- Disable the app. 'service disable bind9' is called. Running 'service is-enable
bind9' and 'service is-enabled named' return errors. App page shows disabled,
there are no errors.

- Repeat tests on Debian stable.

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

plinth/modules/bind/__init__.py

@@ -21,7 +21,7 @@ from .manifest import backup  # noqa, pylint: disable=unused-import
 
 version = 2
 
-managed_services = ['bind9']
+managed_services = ['bind9', 'named']
 
 managed_packages = ['bind9']
 
@@ -97,7 +97,8 @@ class BindApp(app_module.App):
             'daemon-bind', managed_services[0], listen_ports=[(53, 'tcp6'),
                                                               (53, 'udp6'),
                                                               (53, 'tcp4'),
-                                                              (53, 'udp4')])
+                                                              (53, 'udp4')],
+            alias=managed_services[1])
         self.add(daemon)