feat(autoping): autoping availability warning

## Introduced change

A new warning that notifies users when the connected XMPP server
advertises XEP-0199 (urn:xmpp:ping) support but the autoping feature
is disabled in settings. The warning can be toggled with
`/autoping warning on|off`.

The warning fires during the on-connect disco#info exchange, only for
responses from the server's own domain — responses from user JIDs or
subdomain services (e.g., conference servers) are excluded.

### Capabilities

- **On-connect detection**: Warning is emitted automatically when the
  server's disco#info response indicates `urn:xmpp:ping` support while
  autoping is disabled and the preference is enabled (default: on)
- **`/autoping warning on|off`**: Toggle the warning via the existing
  autoping command
- **Domain-scoped**: Only triggers for disco#info from the bound server
  domain; user JIDs and subdomain service JIDs are skipped
- **Case-insensitive domain matching**: Uses `g_ascii_strcasecmp` instead
  of `g_strcmp0` to handle case differences between the stanza `from`
  field and the bound domain
- **Display in settings**: Shown in both `/notify` and `/autoping`
  settings dumps, with consistent alignment and `(/autoping warning)`
  reference in each line
- **Autocomplete**: Dedicated `_autoping_autocomplete` function handles
  the `warning` subcommand with `on|off` completion

## Reasoning behind the change

Users connecting to servers that support XEP-0199 ping but have autoping
disabled may experience poorer connection stability. The warning draws
attention to this configuration mismatch without requiring users to read
documentation or dig into settings.

The warning is scoped to the server domain (not user JIDs or subdomain
services) because autoping is a connection-level feature — it only makes
sense in the context of the server's keepalive capabilities.

The warning preference defaults to `on` so users are informed by default,
but can be disabled with `/autoping warning off` if they prefer not to
see it.

## Implementation details

### Warning logic (`src/xmpp/iq.c`)

`_disco_autoping_warning_message()` is called from the on-connect
disco#info handler when the `from` field matches the bound domain. It
checks three conditions:

1. Server features contain `urn:xmpp:ping`
2. Autoping interval is 0 (disabled)
3. `PREF_AUTOPING_WARNING` is true

All three must be true for the warning to display.

### Domain matching

`g_ascii_strcasecmp(from, connection_get_domain())` is used instead of
`g_strcmp0` to handle case differences. This prevents the warning from
silently skipping if a server echoes the `from` field in a different
case than the bound domain.

### Command integration (`src/command/cmd_*.c`)

- `cmd_defs.c`: Added `/autoping warning on|off` syntax and argument
  description
- `cmd_funcs.c`: Added `warning` subcommand handler that calls
  `_cmd_set_boolean_preference` with `PREF_AUTOPING_WARNING`
- `cmd_ac.c`: Registered dedicated `_autoping_autocomplete` that handles
  the `warning` subcommand with `on|off` boolean completion

### Preference storage (`src/config/preferences.c`)

- Group: `PREF_GROUP_NOTIFICATIONS`
- Key: `autoping.warning`
- Default: `TRUE`

### Settings display (`src/ui/console.c`)

The autoping warning preference is shown in both `cons_notify_setting()`
and `cons_autoping_setting()` with consistent column alignment and a
`(/autoping warning)` reference in each line.

### Tests (`tests/functionaltests/test_autoping.c`)

Six functional tests cover all condition combinations:

| Test | Server ping | Autoping | Warning pref | Expected |
|---|---|---|---|---|
| `autoping_warning_shown_when_disabled` | yes | off | on | warning shown |
| `autoping_warning_not_shown_when_server_unsupported` | no | off | on | no warning |
| `autoping_warning_not_shown_when_autoping_enabled` | yes | on | on | no warning |
| `autoping_warning_not_shown_when_user_disabled` | yes | off | off | no warning |
| `autoping_warning_not_shown_for_user_jid` | yes (from user JID) | off | on | no warning |
| `autoping_warning_not_shown_for_subdomain_service` | yes (from subdomain) | off | on | no warning |

Co-authored-by: Jabber Developer2 <jabber.developer2@jabber.space>

tests/functionaltests/functionaltests.c

@@ -150,6 +150,14 @@ main(int argc, char* argv[])
         PROF_FUNC_TEST(autoping_sends_ping_after_interval),
         PROF_FUNC_TEST(autoping_server_not_supporting_ping),
 
+        /* Autoping availability warning - negative cases wait ~3s */
+        PROF_FUNC_TEST(autoping_warning_shown_when_disabled),
+        PROF_FUNC_TEST(autoping_warning_not_shown_when_server_unsupported),
+        PROF_FUNC_TEST(autoping_warning_not_shown_when_autoping_enabled),
+        PROF_FUNC_TEST(autoping_warning_not_shown_when_user_disabled),
+        PROF_FUNC_TEST(autoping_warning_not_shown_for_user_jid),
+        PROF_FUNC_TEST(autoping_warning_not_shown_for_subdomain_service),
+
         /* Service Discovery - XEP-0030 */
         PROF_FUNC_TEST(disco_info_shows_identity),
         PROF_FUNC_TEST(disco_info_shows_features),

tests/functionaltests/test_autoping.c

@@ -112,3 +112,144 @@ autoping_server_not_supporting_ping(void** state)
     // Should show error about ping not being supported
     assert_true(prof_output_regex("Server ping not supported"));
 }
+
+/*
+ * Autoping availability warning.
+ *
+ * The warning fires from the on-connect disco handler, so the three inputs
+ * (server ping support, autoping interval, warning preference) must all be
+ * set before prof_connect().
+ */
+
+/* Stable substring of the warning text emitted by iq.c. */
+#define AUTOPING_WARNING_MATCH "This server supports XEP-0199"
+
+static void
+_stub_server_disco(gboolean with_ping)
+{
+    if (with_ping) {
+        stbbr_for_query("http://jabber.org/protocol/disco#info",
+            "<iq to='stabber@localhost/profanity' type='result' from='localhost'>"
+                "<query xmlns='http://jabber.org/protocol/disco#info'>"
+                    "<identity category='server' type='im' name='Stabber'/>"
+                    "<feature var='urn:xmpp:ping'/>"
+                "</query>"
+            "</iq>"
+        );
+    } else {
+        stbbr_for_query("http://jabber.org/protocol/disco#info",
+            "<iq to='stabber@localhost/profanity' type='result' from='localhost'>"
+                "<query xmlns='http://jabber.org/protocol/disco#info'>"
+                    "<identity category='server' type='im' name='Stabber'/>"
+                "</query>"
+            "</iq>"
+        );
+    }
+}
+
+void
+autoping_warning_shown_when_disabled(void** state)
+{
+    // All conditions met: server supports ping, autoping off, warning on (default).
+    _stub_server_disco(TRUE);
+
+    prof_input("/autoping set 0");
+    assert_true(prof_output_exact("Autoping disabled."));
+
+    prof_connect();
+
+    assert_true(prof_output_regex(AUTOPING_WARNING_MATCH));
+}
+
+void
+autoping_warning_not_shown_when_server_unsupported(void** state)
+{
+    // Server does not advertise urn:xmpp:ping -> no warning even with autoping off.
+    _stub_server_disco(FALSE);
+
+    prof_input("/autoping set 0");
+    assert_true(prof_output_exact("Autoping disabled."));
+
+    prof_connect();
+
+    prof_timeout(NEGATIVE_ASSERT_TIMEOUT);
+    assert_false(prof_output_regex(AUTOPING_WARNING_MATCH));
+}
+
+void
+autoping_warning_not_shown_when_autoping_enabled(void** state)
+{
+    // Warning is suppressed while autoping is enabled.
+    _stub_server_disco(TRUE);
+
+    prof_input("/autoping set 30");
+    assert_true(prof_output_exact("Autoping interval set to 30 seconds."));
+
+    prof_connect();
+
+    prof_timeout(NEGATIVE_ASSERT_TIMEOUT);
+    assert_false(prof_output_regex(AUTOPING_WARNING_MATCH));
+}
+
+void
+autoping_warning_not_shown_when_user_disabled(void** state)
+{
+    // User opted out -> no warning.
+    _stub_server_disco(TRUE);
+
+    prof_input("/autoping set 0");
+    assert_true(prof_output_exact("Autoping disabled."));
+
+    prof_input("/autoping warning off");
+    assert_true(prof_output_exact("Autoping availability warning disabled."));
+
+    prof_connect();
+
+    prof_timeout(NEGATIVE_ASSERT_TIMEOUT);
+    assert_false(prof_output_regex(AUTOPING_WARNING_MATCH));
+}
+
+void
+autoping_warning_not_shown_for_user_jid(void** state)
+{
+    // disco#info from a user JID (with '@') should not trigger the warning,
+    // only server responses (no '@') should.
+    stbbr_for_query("http://jabber.org/protocol/disco#info",
+        "<iq to='stabber@localhost/profanity' type='result' from='buddy1@localhost'>"
+            "<query xmlns='http://jabber.org/protocol/disco#info'>"
+                "<identity category='person' type='chat' name='Buddy1'/>"
+                "<feature var='urn:xmpp:ping'/>"
+            "</query>"
+        "</iq>"
+    );
+
+    prof_input("/autoping set 0");
+    assert_true(prof_output_exact("Autoping disabled."));
+
+    prof_connect();
+
+    prof_timeout(NEGATIVE_ASSERT_TIMEOUT);
+    assert_false(prof_output_regex(AUTOPING_WARNING_MATCH));
+}
+
+void
+autoping_warning_not_shown_for_subdomain_service(void** state)
+{
+    // disco#info from a subdomain service should not trigger the warning, only the server's own domain should
+    stbbr_for_query("http://jabber.org/protocol/disco#info",
+        "<iq to='stabber@localhost/profanity' type='result' from='conf.localhost'>"
+            "<query xmlns='http://jabber.org/protocol/disco#info'>"
+                "<identity category='conference' type='text' name='Conference Service'/>"
+                "<feature var='urn:xmpp:ping'/>"
+            "</query>"
+        "</iq>"
+    );
+
+    prof_input("/autoping set 0");
+    assert_true(prof_output_exact("Autoping disabled."));
+
+    prof_connect();
+
+    prof_timeout(NEGATIVE_ASSERT_TIMEOUT);
+    assert_false(prof_output_regex(AUTOPING_WARNING_MATCH));
+}

tests/functionaltests/test_autoping.h

@@ -4,3 +4,9 @@ void autoping_timeout_set(void** state);
 void autoping_timeout_zero_disables(void** state);
 void autoping_sends_ping_after_interval(void** state);
 void autoping_server_not_supporting_ping(void** state);
+void autoping_warning_shown_when_disabled(void** state);
+void autoping_warning_not_shown_when_server_unsupported(void** state);
+void autoping_warning_not_shown_when_autoping_enabled(void** state);
+void autoping_warning_not_shown_when_user_disabled(void** state);
+void autoping_warning_not_shown_for_user_jid(void** state);
+void autoping_warning_not_shown_for_subdomain_service(void** state);