Hint about LDAP quota overriding user management quota

[PVince81]

From times to times, people get confused about the fact that setting the LDAP quota attribute or the LDAP default quota will override any quota in the user management page.

The documentation has a note about this, see https://docs.nextcloud.com/server/latest/admin_manual/configuration_user/user_auth_ldap.html and search for "Quota Field".

Now to make this clearer and easy to see, we should:

• docs: move the warning into a warning/note block for "Quota Field"
• docs: add the warning also for "Quota Default"
• add a similar hint for both fields in the LDAP wizard
• also add such hint in the user settings page ? (ideal would be to prevent changing the quota there for LDAP users, but that's more complicated as the UI needs to know about such users)

Thoughts @blizzz ?