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

==================================================
pipe: send/receive data stream through shell pipes
==================================================

``pipe`` commands allow you to send or receive data stream through a Unix shell pipe.
Libervia will create a network connection (using XMPP and Jingle) between you an your
contact.

in
==

Receive data stream. Data will be send to stdout, so it can be piped out or simply print
to the screen. You can specify bare jids of entities to accept stream for, by default all
streams are accepted.

example
-------

Receive a video stream, and redirect it to mpv_ so show the video::

  $ li pipe in | mpv -

.. _mpv: https://mpv.io/

out
===

Send data stream. Data comes from stdin, so you may use pipe in something or just write
some text.

The only expected argument is the full jid of the device where the stream must be piped
out.

example
-------

Send a video to louise::

 $ li pipe out louise@example.org/libervia.123 < some_video.webm

Send output from ``cal`` command to louise::

 $ cal | li pipe out louise@example.org/libervia.123