Provide a viewInApp short URL for alerts

[timroes]

It would be nice to have a URL from the alerting framework to not only view the alert, but triggers its viewInApp mode, i.e. I would like to have a URL like http://kibana.team/alerts/<id>/viewInApp that will open that alert inside the actual app, e.g. if it was a Discover alert it should jump to the corresponding discover view, that you would also go to, when using the "view in app" feature on the alert's detail page.

Why is this relevant? Why can't we simply use the actual link to discover e.g. in the message template? The problem is that the "view in app" links from the classical Kibana applications (Discover, Visualize, Dashboard) might be a) very long and b) contain characters that we know are not parsed well in all messaging tools, since they contain the full state containing e.g. parantheses and commans. Meaning that if we would allow the user to inject that URL into a message, the link might actually not be clickable when they receive the message. Having a unified short link from the alerting framework would solve both issues. We'd always have nice short links and we can guarantee they are always parseable in all tools.

Also we can have this as a shared parameter in all connectors/alert types, thus we don't need every alert type to inject it's backlink URL with a potentially different parameter name and users might get confused why they'd need to use Go to {{backlink}} to view results in an Discover alert, but Go to {{link}} in a Lens alert.

[elasticmachine]

Pinging @elastic/kibana-alerting-services (Team:Alerting Services)

[mikecote]

Moving from 7.x - Candidates to 8.x - Candidates (Backlog) after the latest 7.x planning session.