Make it possible to broadcast events to (web) clients

[ChristophWurst]

Best reviewed together with nextcloud/push#27

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Interesting reads on the topic

https://symfony.com/blog/symfony-gets-real-time-push-capabilities
https://github.com/dunglas/mercure
https://developer.mozilla.org/en-US/docs/Web/API/Server-sent_events
https://laravel.com/docs/5.7/broadcasting#introduction

[rullzer]

Let do this!

[skjnldsv]

Any news? :)

[ChristophWurst]

Any news? :)

Time to review :)

[nickvergessen]

Didn't test, but do you know if this works with http2?
The long polling we currently use in Talk breaks the Nextcloud on http2, because the connection is always kept open.

[ChristophWurst]

I only tested on nginx with http2 and could not see any problems with that. And the fallback does not use long polling but just returns immediately. I think long polling is also problematic in Nextcloud if you use sqlite as one request can block all others do to the single user restriction.

[ChristophWurst]

Didn't test, but do you know if this works with http2?
The long polling we currently use in Talk breaks the Nextcloud on http2, because the connection is always kept open.

Turned out this was caused by a misconfigured apache.

Review time :)

[ChristophWurst]

@daita @juliushaertl @nickvergessen @skjnldsv mind giving this a review? Then I can continue with the part in Push :)

The sooner we get this in the more time there is to experiment and iterate on the API design if necessary.