[whoalin1]

Summary

Document the LDAP POSIX primary-group footgun: matching user/group gidNumber (or AD primaryGroupID) keeps the user in the Nextcloud group even after they are removed via the configured membership attribute.

• Warning on the admin Group Member association field in user_auth_ldap.rst.
• Clarifies the relation is independent of member / memberUid / uniqueMember.
• Notes leftover UI/occ membership, that ldapGidNumber is configurable but not in the UI, and that ldap:show-remnants does not clear this secondary relation.

Closes #11148

Test plan

• Sphinx build of the admin manual succeeds for user_auth_ldap.rst
• New .. warning:: appears after Group Member association and before Nested groups
• Mentions gidNumber, independence from assoc attr, AD primaryGroupID, ldapGidNumber, and that show-remnants is unrelated
• No cleanup / API pages changed

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AI disclosure

This PR was drafted with the help of AI coding assistants (Cursor agents / LLM-based tools), including the description. I am responsible for it and happy to rework anything that doesn't fit.

All commits carry an Assisted-by: Cursor:grok-4.7 trailer.

[come-nc]

Suggested change

	Prefer distinct ``gidNumber`` namespaces for users versus groups, or
	change the user's ``gidNumber`` / ``primaryGroupID`` when membership
	should end. ``ldap:show-remnants`` only lists deleted users and does not
	clear this secondary relation.

I do not understand this part and why it mentions show-remnants.
The rest of the changes look good.

[whoalin1]

Thanks @come-nc, I applied your suggestion and removed that paragraph in c17a053.

AI disclosure: this PR and reply were drafted with help from an AI assistant (Assisted-by trailer on the commits).

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