mdo.1: Document group-related and fine-grained control functionalities

[olce]

Summary

This is a manual page update describing the functionality that was added
to mdo(1) in commit 3ca1e69028ac ("mdo(1): Add support and shortcuts for
fully specifying users and groups"). Please either refer to that commit
or the new manual page's content for more information.

While here:

• Add to the introduction a description of process credentials and some specific vocabulary that is used throughout the page, as well as the relationship between mdo(1) and mac_do(4).
• Update the HISTORY section.
• Add AUTHORS and SECURITY CONSIDERATIONS sections.

MFC after: 1 hour
Sponsored by: The FreeBSD Foundation
Sponsored by: Google LLC (GSoC 2025)
Co-authored-by: Kushagra Srivastava <[e-mail]>

[ziaee]

usr.bin/mdo/mdo.1

4–12

I think this can and should be done, because it preserves everything but makes it more clean. We must be allowed to make things more clean. However, @emaste has told me I can't touch whitespace here, so maybe @bapt should approve this too.

38–39

I think this last paragraph should maybe be part of the introductory paragraph.

"The mdoc utility executes the passed command, or an interactive SHELL, with the requested process credentials."

Except what I just wrote in quotes is really ugly >.<

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132

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[emaste]

usr.bin/mdo/mdo.1

4–12

No this is fine, although @bapt is free to comment here as well if he wants

[olce]

usr.bin/mdo/mdo.1

38–39

Having that paragraph near the top indeed evacuates the topic, and is then followed only by a discussion of options and credentials, which makes this independent aspect stand out and might help general understanding.

Your comment also makes me notice that we (actually, Kushagra) introduced the word "interactive", which strictly speaking is wrong and should be removed (even if the canonical use case will be to launch an interactive shell).