nuageinit: Add support for uid

[zenzesama_gmail.com]

Summary

Adds support for specifying an explicit UID when creating users through nuageinit. Both numeric and string UID values are supported. Invalid or negative UIDs are rejected. The new uid option is documented in nuageinit(7). Existing automatic UID allocation remains unchanged when no UID is specified. A UID already in use or out of range is left to pw(8) to reject.

PR: 293716
Reported by: Einar Bjarni Halldórsson <[e-mail]>
Signed-off-by: Kushagra Chauhan <[e-mail]>

Test Plan

• adduser_uid passes with the change and fails without it.
• Verifies numeric UID 1600 and string UID "1601" are correctly assigned.
• Verifies that a negative UID is rejected and the corresponding test user is not created.
• Without the change, UIDs 1001 and 1002 are allocated instead, and the test user is created.
• adduser and adduser_passwd continue to pass.

[bapt]

don't forget to bump the date in the manpage while pushing and please MFC this in 15.2! thanks a lot

[zenzesama_gmail.com]

Thanks for the review! For whoever lands this, please use Kushagra Chauhan <[e-mail]> as the author. The commit message is in the summary.

[dtxdf]

LGTM!

[emaste]

git-arc patch figures it out: Making best guess: Turning zenzesama_gmail.com to Kushagra Chauhan <[e-mail]>