fix(omemo): bootstrap device list on prosody-class servers

Two gaps kept /omemo gen from ever publishing on a fresh account:

- _omemo_receive_devicelist() only recognised the legacy code='404'
  error attribute as "node does not exist". Prosody sends the RFC 6120
  <item-not-found/> condition instead, so the empty-list bootstrap never
  ran. Accept the defined condition too, and log the expected bootstrap
  case at debug instead of error.

- connection_request_features() disco'd only the server domain, but
  XEP-0163 PEP services (including pubsub#publish-options) announce
  their features on the account's bare JID. Query the bare JID as well,
  registering it in the feature table, so connection_supports() sees
  PEP features.

Fixes #169

src/xmpp/connection.c

@@ -658,6 +658,15 @@ connection_request_features(void)
     /* We don't record it as a requested feature to avoid triggering th
      * sv_ev_connection_features_received too soon */
     iq_disco_info_request_onconnect(conn.domain);
+
+    const char* barejid = connection_get_barejid();
+    if (barejid && g_strcmp0(barejid, conn.domain) != 0) {
+        if (!g_hash_table_contains(conn.features_by_jid, barejid)) {
+            g_hash_table_insert(conn.features_by_jid, strdup(barejid),
+                                g_hash_table_new_full(g_str_hash, g_str_equal, free, NULL));
+        }
+        iq_disco_info_request_onconnect(barejid); // XEP-0163: PEP services announce features on the account's bare JID
+    }
 }
 
 void

src/xmpp/omemo.c

@@ -446,18 +446,21 @@ _omemo_receive_devicelist(xmpp_stanza_t* const stanza, void* const userdata)
     GList* device_list = NULL;
 
     if (g_strcmp0(type, STANZA_TYPE_ERROR) == 0) {
-        log_error("[OMEMO] can't get OMEMO device list");
         xmpp_stanza_t* error = xmpp_stanza_get_child_by_name(stanza, "error");
         if (!error) {
             log_error("[OMEMO] missing error element in device list response");
             return 1;
         }
 
+        // a missing node is signalled via legacy code='404' or the RFC 6120 <item-not-found/> condition
         const char* code = xmpp_stanza_get_attribute(error, "code");
-        if (g_strcmp0(code, "404") == 0) {
+        if (g_strcmp0(code, "404") == 0
+            || xmpp_stanza_get_child_by_name_and_ns(error, STANZA_NAME_ITEM_NOT_FOUND, STANZA_NS_STANZAS)) {
+            log_debug("[OMEMO] no devicelist node for %s, bootstrapping an empty one", from);
             omemo_set_device_list(from, NULL);
             return 1;
         }
+        log_error("[OMEMO] can't get OMEMO device list");
     }
 
     xmpp_stanza_t* root = NULL;