[APM] Getting started: Change logic to check whether APM Server was setup when running under fleet

[simitt]

Description
When APM Server is started with the new indexing strategy (apm-server.data_streams.enabled=true) it does not write an onboarding document. The whole APM Setup process moves to Kibana and Fleet and therefore Fleet Status should be used to check whether the APM Integration (including the APM Server) is properly setup.

Required Action
Remove the button to check whether APM Server was setup in the Fleet install section (described in #88659), but explain to users how to check if the APM Server is running under Fleet.
We should give a short desription and link to the Quick Start guide, which will include the APM quickstart.
Details in #86462 (comment)

[elasticmachine]

Pinging @elastic/apm-ui (Team:apm)

[ruflin]

If I remember correctly, the apm-server doc was written as soon as the first time the apm-server was set up. It was basically to indicate to the user, that he has a working apm-server. So in the new scenario, this means having at least 1 policy with an apm integration inside that was successfully deployed. @nchaulet Do we have an API endpoint for this?

If we check for the above, the behaviour will slightly change. So if the user did the setup and then stops apm-server again, it will show in the APM UI again that there is no apm-server and tells him to go to Fleet UI to set it up. We can go even further to tell users, he doesn't have an Elastic Agent enrolled yet and should go fleet.

For some time, there is a hybrid approach needed, because it might be that the standalone apm-server is used.

An, there is also the option, that Elastic Agent with apm-server is standalone and does not have the permission to write the doc. What are we doing in this scenario?

[simitt]

Elastic Agent with apm-server is standalone

We only plan to support APM Server via Elastic Agent in fleet modus, so we don't have to take precautions for that.

[simitt]

My comment from above was not quite right, rephrasing with a cite from the APM Server 8.0 vision doc:

As with any Elastic Agent integration, it is technically possible to run with Fleet or standalone. Fleet mode is required in order to install APM-specific templates and other package artifacts, as well as to support features such as central configuration and server status.

[sorenlouv]

Moving this to 7.13

[sorenlouv]

This might not be needed. @simitt will close or clarify if it's still needed.

[simitt]

Remove the button to check whether APM Server was setup in the Fleet install section (described in #88659), but explain to users how to check if the APM Server is running under Fleet.
We should give a short desription and link to the Quick Start guide, which will include the APM quickstart.

Here is how you can familiarize yourself with the steps involved:

(1) Navigate to Fleet UI and check for the policy that should be used (if user has not yet set up an Elastic Agent, they will only see the default policies)

(2) Check whether APM integration is added to the desired policy, if not add it

(3) Enroll an Elastic Agent to the desired policy, which will then run the APM Server

[sorenlouv]

Replaced by #100672