Dev3.0.15 generate external_videos.xml for playing on the fly

[hiroshisuga]

What does this PR do?

Generate external_videos.xml for play it back on the fly.
See: bigbluebutton/bbb-playback#127
You need to directly modify the script
/usr/local/bigbluebutton/core/lib/recordandplayback/generators/events.rb and
/usr/local/bigbluebutton/core/scripts/publish/presentation.rb and
/usr/local/bigbluebutton/core/scripts/presentation.yml

This PR is necessary for hiroshisuga/bbb-playback#39 .

See also the never-merged PR bigbluebutton#18222 for description.

Closes Issue(s)

Closes #

Motivation

More

Still to do:
Since BBB3.0 using GraphQL, the event.xml items related to external video have been massively reduced.
For instance,

• type="presenterReady" and type="play" events are not issued when the video is initially loaded, so the video does not start automatically.
• type="play" events are only called when the user stop and start the video (this happens when user skips the video by operating the slider).
• type="playerUpdate" events are not issued, instead, type="playbackRateChange" is used for changing rate.
• previously the type="playerUpdate" events are issued every second to synchronise the video. As they are not issued anymore, video synchronization is more problematic.
• A perhaps new event type="seek" has been introduced (needs research on what it means).
• Since BBB3.0, the externalvideostop event is always called when a screenshare start, inserting an unnecessary externalvideostop event in the event.xml. This may break the recording logic (see [3.0] external video not recorded (URL not shown) after screenshare bigbluebutton/bigbluebutton#23986 and 2fd5a81)

We need to recover or make some workaround in the record_and_playback module to make it fully working.
On the other hand, we may have new events implemented since 3.0 (probably only 'seek' event). Need a research.

The easiest option is to change the player:
https://github.com/hiroshisuga/bbb-playback/blob/abe1b59883de8f3a80b1deb5ac42d72aae4a6c2e/src/components/external-video-player/index.js#L237-L313

[github-actions]

This pull request has conflicts ☹
Please resolve those so we can review the pull request.
Thanks.