[NEW] Multiple slackbridges

[Hudell]

Closes #9339

This PR adds support for multiple slack bridges on the same RC server.

[smellems]

Thanks @Hudell! This is related to #10915 as well.

Question: how will this work where channels in multiple Slackbridges have the same name? ex.: #general

Right now, channels names have to match in Rocket.Chat and Slack for the bridge to work.

[Hudell]

Channel names still need to match. If there are two slackbridges with a channel with the same name, both will work together in the same RC channel. However, Rocket.Chat will not send messages received from one Slackbridge to the others.

[creaux]

What left on this PR?

[Hudell]

The only thing missing is an area on the administration center to configure multiple slack servers.

[TimHarrison]

Any update on the build out of the admin setting page to complete this effort? It's been over a month since any visible progress was made on this feature. By the sounds of it, this feature is highly desirable by many people and organizations, including me. I'm sure the completion of this feature would make a lot of people happy!

[Sing-Li]

@TimHarrison We are making some overhauling changes ("improvements") on the Admin UI and the remaining work on this PR hinges indirectly on it.

@TimHarrison @creaux One solution to enable some of you to move forward with this -- is to enable configuration via some hard code in the meantime. Are you guys on a fork that you can pull down this PR and work with us to make it work for you? [anyone else in such a position and wants to be early adopters - please also comment here] Thanks.

[Hudell]

I changed the API Token setting to accept multiple lines, so you can add as many API tokens as you need and RC will connect to each of them individually. With this, there's no need to change any code to test the multiple slack bridges.

[Ismaw34]

Maybe this PR #12213 could be added to this?