1199: Add notify

[ztefanie]

Short description

Add notify command and end all jobs with it.

Notify only works if the toolbelt was installed successfully.
The toolbelt is only notifying if it was a main branch or if it is a branch starting with "release-" and the "allow-all-branches" flag is set.

Resolved issues

Fixes: #1199

[f1sh1918]

Just one question because i didn't find it in the code @ztefanie
Is there also a notification for successful release? because it was mentioned in #1199 or will there be a separate pr

[ztefanie]

Just one question because i didn't find it in the code @ztefanie Is there also a notification for successful release? because it was mentioned in #1199 or will there be a separate pr

yes there will be a separate PR, i will open a ticket for this. We need the release-notes parsing first.

[f1sh1918]

nicely done :)