[Request] Fleet integrations index template structure

[joshdover]

Description

Fleet installs index templates for integration data streams in a specific structure, one that has changed over several releases and we have future changes planned. We should have this structure documented for each version to help users know what each template is for and which are editable by the user. This related to, but an extension of elastic/observability-docs#1578

Collaboration

• The product team will provide the initial content and the docs team will edit / review

The current structure as of 8.2 is documented in the "existing scheme" section of elastic/kibana#121118

Contact Person: @hop-dev

Suggested Target Release

(Let us know if this feature is needed for a specific release.)

Stakeholders

(Please list any stakeholders for this issue.)

[hop-dev]

I have created a dev doc in the meantime covering some of this.

elastic/kibana#128896

[joshdover]

Prioritizing this low for now while we work on changes in this area: elastic/kibana#121118

[dedemorton]

I wonder if we can provide some general guidance without documenting a structure we know is changing. Or maybe we should wait until the structure is less volatile.

I assume there's a strong use case that requires users to edit the index templates. The docs should describe why you'd want to edit the index templates and the implications of changing them.