Flag channels by type

[mld18]

Rocket.Chat Version: 0.55.1
Running Instances: 1
DB Replicaset OpLog: Disabled
Node Version: v4.2.6

We need a way to distinguish certain types of channels. Ideally, the users have a clear visual distinction in the channel list.

In our case we would like to flag channels that are supervised. This is important for chat at organizational scale. This way users know whether they can formally address topics or the channel is just for a casual chat with colleagues.

My idea would be to allow for the definition of channel tags/flags. The tags/flags could have a custom CSS class assigned. In the channel list Rocket can attach the respective CSS class to the elements that wrap the channel names. In the header section of the channel view the tags/flags may be shown with shortnames similar to the tags in GitHub.

Example for styling based on custom channel CSS class (#feedback is the distinguished channel in this example):

[mld18]

This one relates to #2049. The resolution of #2049 would probably solve this issue to a great extend. Well, except for the posibility of a distinguished visual styling.

[marceloschmidt]

Relatable: RocketChat/Rocket.Chat#658