backend, frontend: prepare remote control: This is a series of changes necessary to prepare the implementation of remote control feature: - XEP-0166: add a `priority` attribute to `ApplicationData`: this is needed when several applications are working in a same session, to know which one must be handled first. Will be used to make Remote Control have precedence over Call content. - XEP-0166: `_call_plugins` is now async and is not used with `DeferredList` anymore: the benefit to have methods called in parallels is very low, and it cause a lot of trouble as we can't predict order. Methods are now called sequentially so workflow can be predicted. - XEP-0167: fix `senders` XMPP attribute <=> SDP mapping - XEP-0234: preflight acceptance key is now `pre-accepted` instead of `file-accepted`, so the same key can be used with other jingle applications. - XEP-0167, XEP-0343: move some method to XEP-0167 - XEP-0353: use new `priority` feature to call preflight methods of applications according to it. - frontend (webrtc): refactor the sources/sink handling with a more flexible mechanism based on Pydantic models. It is now possible to have has many Data Channel as necessary, to have them in addition to A/V streams, to specify manually GStreamer sources and sinks, etc. - frontend (webrtc): rework of the pipeline to reduce latency. - frontend: new `portal_desktop` method. Screenshare portal handling has been moved there, and RemoteDesktop portal has been added. - frontend (webrtc): fix `extract_ufrag_pwd` method. rel 436

--- a/libervia/backend/plugins/plugin_xep_0353.py	Sat May 11 13:25:45 2024 +0200
+++ b/libervia/backend/plugins/plugin_xep_0353.py	Sat May 11 13:52:41 2024 +0200
@@ -16,11 +16,13 @@
 # You should have received a copy of the GNU Affero General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
+from typing import cast
 from twisted.internet import defer
 from twisted.internet import reactor
 from twisted.words.protocols.jabber import error, jid
 from twisted.words.protocols.jabber import xmlstream
 from twisted.words.xish import domish
+from libervia.backend.plugins.plugin_xep_0166.models import ApplicationData
 from wokkel import disco, iwokkel
 from zope.interface import implementer
 
@@ -328,6 +330,12 @@
             log.warning("No application specified: {message_elt.toXml()}")
             return
 
+        cast(list[tuple[domish.Element, ApplicationData]], desc_and_apps)
+        desc_and_apps.sort(
+            key=lambda desc_and_app: desc_and_app[1].priority,
+            reverse=True
+        )
+
         session = self._j.create_session(
             client, session_id, self._j.ROLE_RESPONDER, peer_jid, local_jid
         )