feature request: make notifications more configurable

[gecube]

Good day Sirs!

I was struggling to make a telegram notification working, but I found a way to enable it. The screenshot is below:

Unfortunately, we can see that I could not easily without any additional external entities split the incident and deployment messages. Even more - if I want to deliver messages to different teams channel and separate them by project, it is not obvious how to do it.

My suggestions are the next:

• first of all allow multiple integrations of the same type simultaneously

Right now I can set up only 1 webhook reciever, 1 slack receiver etc. But from UI side it looks like that different types of receivers could coexist and the event would be sent to all receivers simultaenously

• make a proper UI with constructor - so user would be able to add as many receivers as he wants.
• prepare an option to make a more granular receiver settings - let's say allow incidents to come into one channel of slack and deployments into another.

I am open to discussion how it should look like. Or maybe no action should be taken and the best option would be to deploy alert manager next to coroot and make all event routing through it - but then we need a clear and proper examples and documentation how it could be implemented.