[Synthetics] Clarify how stand alone agents should be used

[paulb-elastic]

Description

The current documentation states that Synthetics should only be used with Agents enrolled in Fleet.

Whilst this is true for the majority of cases, there is a mechanism where stand alone Agents may be needed (such as in K8 environments with auto discovery). This cannot be used with the Synthetics App or workflow, but may still be a reasonable solution for those that need it, relying on Uptime, or custom dashboards.

This should be documented so that users requiring this can see examples of how to use the product in this way.

Resources

This is a replacement requirement for https://github.com/elastic/observability-docs/issues/2859, as we intend to document this use case for working with Agent in standalone mode for Synthetics.

Collaboration

The product team will provide the initial content.

Point of contact.

Main contact: @andrewvc

Stakeholders:

• @paulb-elastic

[colleenmcginnis]

@paulb-elastic @andrewvc would this way of using the product fit into the "advanced considerations" doc Andrew started in https://github.com/elastic/observability-docs/pull/2989? Would it make sense to mention that using stand alone agents is possible on the Monitor resources on private networks, then link to the advanced considerations doc for more details?

[paulb-elastic]

Adding it to the advanced page seems reasonable to me.

I think you're right, we'd have to link from that page you mention too as we currently say "don't do it", so that gives mixed messages and likely to be confusing if people read each page in isolation,