[SECURITY SOLUTIONS] [Case everywhere] Move Insert Timeline functionality to Cases

[stephmilovic]

Move (or pass as arg) the insert_timeline functionality from Security Solution to Cases

[elasticmachine]

Pinging @elastic/security-threat-hunting (Team:Threat Hunting)

[patrykkopycinski]

maybe we could expose an API to register custom markdown editor plugins, so that way we could keep functionality related to the timeline inside the security solution and also allow to register custom plugins from other solutions in the future?

[cnasikas]

@patrykkopycinski I agree, it would be nice to have that functionality. A problem that could occur with that approach is the support and maintenance of each markdown plugin. Who gonna own the markdown plugin? Cases or the solution that created? Also it gets a bit more complex when you take into account how is gonna being shown in external services as Jira or ServiceNow. An alternative would be to not expose an API but to review PRs from others when they want to create their markdown plugin and put it in our codebase.

[michaelolo24]

Just noting this conversation continued on over on the PR #96496, and have made the move to just pass the timeline specific functionality through for now.