Add config option for CORS headers to support cluster proxy setup

[schrd]

Cluster proxy setup required correct CORS headers to move notes to whiteboard. This patch adds an option to configure it. To configure it add a file /etc/bigbluebutton/etherpad.json with similar content:

{
	"cluster_proxies": [
		"https://bbb-proxy.example.org"
	]
}

related to bigbluebutton/bigbluebutton#15457
related to bigbluebutton/bigbluebutton#15753

[pedrobmarin]

I'm surprised Etherpad does not have a built-in solution for this...
Quick question, tho: does BBB leverages Etherpad settings json file with a softlink for it in /etc?
Asking because you could use that file to store this CORS configuration. No need for adding a hardcoded filepath in that case.

[schrd]

I did not find something builtin in etherpad. See https://github.com/ether/etherpad-lite/blob/develop/src/node/hooks/express/importexport.js#L45

And I chose to use a seperate config file because settings.json is shipped by packages and is not marked as a config file. Usually settings.json does not have to be adjusted and the CORS setting is IMHO the only thing that has to be configured in etherpad. If the package ships updated settings, nothing has to be adjusted on the machine and no settings have to be merged. I think it is the most operator friendly solution.

[pedrobmarin]

I usually wait for @alangecker to check on this but I'm not sure about his availability right now. So I'm merging this one and maybe we can re-discuss about transfering the Etherpad libs to the BBB account.
cc @ffdixon @prlanzarin

[alangecker]

@pedrobmarin I'm currently rather limited in what I can contribute to BBB, I would therefore be happy if we could move these libs to the BBB account! 🙂

If I try to transfer it by myself, I get following error:

You don’t have the permission to create public repositories on bigbluebutton

If someone (@ffdixon? 🙂) could provide me with that permission temporarily I could transfer them over

[ffdixon]

Hi @alangecker, I've created https://github.com/bigbluebutton/bbb-etherpad-plugin and made you a maintainer. Don't hesitate to reach out if you need anything more.

[GuiLeme]

Hey guys, I would like to know the status here, this was already merged, but is it already applied in BBB? I am asking this in order to proceed with the tests and review of this PR: bigbluebutton/bigbluebutton#15457 and also, to close this other one: bigbluebutton/bigbluebutton#15753.

[schrd]

Hi @GuiLeme I built BBB 2.6 beta 1 packages from source and this patch is included. IMHO bigbluebutton/bigbluebutton#15753 can be closed and bigbluebutton/bigbluebutton#15457 can be merged :-)