Emails sent from Kibana Alerting to have a footer with a link back to the alert details

[mikecote]

As a split from the original issue #49392. It would be nice for all the emails that are generated from Kibana alerts to have a footer with a link back to the alert details page. This would remove the requirement for the user to manually enter a URL within their message.

The approach like GitHub email notifications is what I originally had in mind. A "View in Kibana" link at the bottom or something along those lines.

NOTE:
This will depend on #45815 but work can be started in parallel.

[elasticmachine]

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

[mikecote]

This may depend on something like #45815 to work for alerts created via the HTTP APIs, pre-configured alerts, etc.

[mikecote]

cc @arisonl

[pmuellr]

Thinking about how this should work.

Wondering if the thought here helps: #66095 (comment)

Maybe yes? So the default action message we calculate could return an additional bit at the bottom with the relevant link in it?

Longer-term, I keep in mind the multi-step action story of "create GH issue" -> "send email", where the email should have a link to both the alert details AND the GH issue, so I think this gets complex.

Maybe we need to have top-level support for something like a links action param, which would be an array, and we'd pre-fill one for alerts pointing to the alert details, other alerts (and previous actions) could add additional links to their solution pages or whatever. Actions would then be responsible for rendering these as appropriate, which would be appending to the bottom of the message, typically. The links elements would need to have some message text to render beside the link (and perhaps some anchor text, eh, that will get complicated) as well as the link itself.

Eg,

actionParams.links.push({ message: 'alert details:', link: 'http://example.com' })
scheduleAction(... actionParams ...)

I think today, all our actions would be fine if they just rendered this as alert details: http://example.com (ie, plain text, slack markdown, email markdown), but if we end up having an action that requires html formatting, it would need to be alert details: <a href='http://example.com'>http://example.com</a> - seems like we need to consider such things - allow the action to do the final formatting.

Not directly related, but I believe we'll also want a message "prefix" and "suffix" as well, for folks who need to put some kind of disclaimer on all their notifications. This seems more "global" than "alert-specific", but something to keep in mind ...