[Security Solution][Expandable flyout] - add onClose to the API to let developers know when the expandable flyout is being closed

[PhilippeOberti]

Summary

This PR adds an onClose property to the kbn-expandable-flyout package. Until now, there was not any way to know when the expandable flyout was being closed. This was due to the fact that the expandable flyout is a wrapper of the EUI flyout, and has its own api.

Approach

This approach implements an rxjs observable that the kbn-expandable-flyout package provides through its API. The observable is triggered every time the flyout closes. Components can listen to the observable and run the code they need.
Because there can be multiple flyouts open at the same time, the observable emits the id of the flyout. It its current state within Security Solution, only 3 options here can be emitted:

• flyout for the expandable flyouts open on the alerts page, the cases page or the explore pages (host/user...)
• timelineFlyout for the expandable flyout from a Timeline
• memory for the expandable flyouts opened in memory mode (like the one on the rule creation page)

Notes:

One downside of this approach is we're running the risk to have developer forgetting to unsubscribe from the observable and therefore introducing memory leaks...
An alternative approach PR will be open shortly to investigate using Events instead of Observables.

Will help
https://github.com/elastic/security-team/issues/7670 and #179520

Checklist

• Documentation was added for features that require explanation or tutorials
• Unit or functional tests were updated or added to match the most common scenarios

[elasticmachine]

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

[PhilippeOberti]

@christineweng @logeekal @lgestc I opened this new PR in favor of this other one so we can focus only on the onClose API exposed by the kbn-expandable-flyout.

It will be easier to discuss the rxjs Observable vs Event approach

[kibana-ci]

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Metrics [docs]

Async chunks

Total size of all lazy-loaded chunks that will be downloaded as the user navigates the app

id	before	after	diff
securitySolution	15.1MB	15.1MB	+260.0B

Unknown metric groups

API count

id	before	after	diff
@kbn/expandable-flyout	38	39	+1

History

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@elasticmachine merge upstream