Add documentation how to avoid data modification by tools

[bernt-matthias]

While working on #14235 I thought this might be a nice addition to the docs.

Not entirely sure if real_system_username will work for non DRMAA job runners?

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[hexylena]

Suggested change

	For both more information can be found in the [job configuration](jobs.md) documentatiion and see also [using a compute cluster](cluster.md).
	More information on pulsar configuration can be found in the [job configuration](jobs.md) documentation, and the other two are explained in [using a compute cluster](cluster.md).

[hexylena]

I'm not sure it's enough information for the pulsar option, jobs.md doesn't really cover much right? Would it maybe be useful to link to https://training.galaxyproject.org/training-material/topics/admin/tutorials/interactive-tools/tutorial.html#securing-interactive-tools (or better, have us extract that pulsar bit and link to that?)

[bernt-matthias]

I'm fine with both, but don't feel competent wrt pulsar to move the pulsar bit from GTN.

[natefoo]

It might be good to have a top level "Security Considerations" page that this goes on to? Otherwise, I like this a lot, it's something that some admins eventually learn but that we definitely should have been more explicit about up front.

[github-actions]

This PR was merged without a "kind/" label, please correct.