Make blocknote configurable as shared notes editor.

[tibroc]

As of BBB v3.0.25 blocknote can be used as a replacement for etherpad in the shared notes. This commit adds the option to select the shared notes editor.

I did not add the option for a config override file for blocknote (compare https://github.com/bigbluebutton/bigbluebutton/pull/24519/changes#diff-3cb944e426b15411f0accb25bd2df64a2901926872c3270894e0d338143b890e), because I do not see the need at the moment.

[BrutalBirdie]

LGTM!

[defnull]

Nitpick, but can you make blockNote lowercase (or change tests to be case-insensitive) and add a test that warns if there is an invalid value to prevent typos there?

Also, if I remember correctly, the proxy mixin would need some additions for this to work in a proxy cluster setup. Maybe move the cluster-proxy stuff to the proxy mixin instead of a separate file? I'd like to keep everything that needs to change for a proxy mode in one file, do be able to compare it with the official documentation more easily.

[tibroc]

@defnull I accounted for both comments. What I did not do is make the whole etherpad config optional depending on if you use blocknote. Since I am guessing that blockenote will become the default sooner than later, I am guessing this is ok?

[defnull]

Hmmmm. I just noticed that both can be installed at the same time and also used at the same time (dynamically selected during the meeting create call), which means that we actually have to keep etherpad installed and configured. So, the PR can be merged I think. I'll try to test and merge this week.

Once blocknote is stable, we can switch things around and make etherpad optional, or remove it entirely. We can be a little bit opinionated with this role I think. If something is clearly the better better, then there is no reason to continue supporting the other options.