Documentation to explain the use of @custom component template

[gemaliano]

Describe the enhancement:
To include in documentation who are the @custom component template and how customers can use them.
The @custom component template are for the users to make custom modifications.
Documentation we have is related to ingest pipelines: https://www.elastic.co/guide/en/fleet/8.5/data-streams-pipeline-tutorial.html#data-streams-pipeline-four

Describe a specific use case for the enhancement or feature:
Are @custom component going to survive upgrades?

[kilfoyle]

@cmacknz Do you think someone from the Elastic Agent team might be able to demo the custom component templates? That would really help me to get some docs together for this issue.

[cmacknz]

This would be an integrations feature, @kpollich would know who knows the most about the underlying implementation.

[kpollich]

Yep this is something my team can help with. @jen-huang is this something you could take a pass at drafting docs for?

Are @Custom component going to survive upgrades?

Yes @custom templates and pipelines are fully user-managed, and will not be altered, removed, etc by integration upgrades.

[jen-huang]

@kpollich Yeah I can draft docs for this. When does it need to be done?

[kilfoyle]

@jen-huang This issue has been in the docs backlog since 2022 so I don't think it's urgent but it would definitely help users. Thanks a lot for offering to draft something up!

[jen-huang]

Thanks @kilfoyle. @kpollich I put this in the next sprint and assigned myself to make sure I don't forget.

[bmorelli25]

This might be done. @alexandra5000 will look into this.