mumble: Add diagnostic for setup config changes

Tests:

- Modify or remove the sslCert/sslKey lines in mumble-server.ini. The
  diagnostic is failed. After repair, the expected lines are restored,
  and the diagnostic is passed.

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

plinth/modules/mumble/__init__.py

@@ -7,10 +7,12 @@ import pathlib
 
 from django.urls import reverse_lazy
 from django.utils.translation import gettext_lazy as _
+from django.utils.translation import gettext_noop
 
 from plinth import app as app_module
 from plinth import frontpage, menu
 from plinth.daemon import Daemon
+from plinth.diagnostic_check import DiagnosticCheck, Result
 from plinth.modules import names
 from plinth.modules.backups.components import BackupRestore
 from plinth.modules.firewall.components import Firewall
@@ -113,6 +115,12 @@ class MumbleApp(app_module.App):
         privileged.setup()
         return True
 
+    def diagnose(self) -> list[DiagnosticCheck]:
+        """Run diagnostics and return the results."""
+        results = super().diagnose()
+        results.append(_diagnose_config())
+        return results
+
 
 def get_available_domains():
     """Return an iterator with all domains able to have a certificate."""
@@ -140,3 +148,10 @@ def get_domains():
         return [domain]
 
     return []
+
+
+def _diagnose_config() -> DiagnosticCheck:
+    """Check that configuration changes made during setup are in place."""
+    result = Result.PASSED if privileged.check_setup() else Result.FAILED
+    return DiagnosticCheck('mumble-config',
+                           gettext_noop('Mumble server is configured'), result)

plinth/modules/mumble/privileged.py

@@ -25,6 +25,15 @@ def setup():
     aug.save()
 
 
+@privileged
+def check_setup() -> bool:
+    """Check that setup configuration is retained."""
+    aug = _load_augeas()
+    ssl_cert_matches = aug.get('.anon/sslCert') == DATA_DIR + '/fullchain.pem'
+    ssl_key_matches = aug.get('.anon/sslKey') == DATA_DIR + '/privkey.pem'
+    return ssl_cert_matches and ssl_key_matches
+
+
 @privileged
 def set_super_user_password(password: secret_str):
     """Set the superuser password with murmurd command."""