[Request]: Update APM docs to reflect changes related to the Elasticsearch apm-data plugin

[colleenmcginnis]

Description

In 8.15, the APM team moved index templates, component templates, and ingest pipelines from the APM integration package to a new Elasticsearch apm-data plugin. The APM integration package is now an input-only package meaning that the package would not define any data streams.

Here's my understanding of how this will impact the docs (please correct me if I'm wrong!):

• When a user sets up the APM Server binary, they used to have to install the APM integration. Now users using the APM Server binary shouldn't have to install or work with the APM integration at all because the functionality the APM integration was providing is now built into Elasticsearch (i.e. the apm-data plugin).
• When a user sets up a Fleet-managed APM Server, how the APM integration works behind the scenes changes with the addition of the Elasticsearch apm-data plugin, but the workflow for getting a Fleet-managed APM Server initially set up will not change so the docs on getting set up don't need to be updated.
• Users using either the APM Server binary or Fleet-managed APM Server will need to know about how the Elasticsearch apm-data plugin works and how the APM integration's role has changed if/when they are customizing index templates, component templates, or ingest pipelines.
• In addition to updates in the Observability guide, the integration docs probably also need to be updated.

My next step is to go through individual docs to determine which need to be updated based on these principles ☝ and open a draft PR for the APM team to review.

Resources

Here's what I've found:

• @carsonip got a head start on this in Update docs after migrating from apm integration package to ES apm-data plugin in 8.15 #4239 (mostly in content specifically about data streams)
• @endorama opened Update docs to remove requirement for installing the integration apm-server#13237 to update the docs, which has some context and links to Switch apm integration package to input-only package apm-server#11529

Which documentation set does this change impact?

Stateful and Serverless

Feature differences

@simitt can you confirm that this works the same way in stateful and serverless?

What release is this request related to?

8.15

Collaboration model

The documentation team

Point of contact.

Main contact: @carsonip? (feel free to tag others as needed)

Stakeholders: TBD