Element-android: Feature: Separate custom room notification

[matrixes]

A thing I'm missing in Android-Riot is notification customisability.
In that app it's possible to choose more generic notification settings, such as when my username is mentioned, when a message is sent to a room I'm a member of, etc.

What I'd _also_ like to have is a way of customising what sound a room makes that matches any of those notification rules. This way I'll be able, by noise alone, to discern what/who wants to reach me.
It would also be useful to have the generic rules customised per room, instead of the much more global context that's applied in Android-Riot.

[bmarty]

First part is handled by #395, the two other parts could be implemented (but in a far future for RiotX...)

[T-bond]

I would also like this feature very much. Setting different notification sound per room basis.

Another idea would be that all room by default would be in a notification category noisy, and when the user wants to change a room there would be a toggle to create a separate notification channel for it. So it would be fully customisable.
Two question arises about this: How would it work pre notification channels android, and how would this work with another client's settings.

But if the old Riot way of notification system stay, I still would like to see a custom notification sound as on the Web version. (Especially if the sounds can be automatically synchronised with the clients. But maybe this would be a drawback. It needs implementation and if the user would like to use a different notification for different clients but for the same room it would not allow it.)

Maybe this is related to: #169

[jtrees]

If this means I can set a custom notification sound for messages from a particular user, then I want this.