net-mgmt/netbox: Update to 4.2.8

Changelog:

Enhancements:

• Introduce the --readonly flag on upgrade script
• Add trace buttons to terminations under cable view
• Enable filtering prefixes by group of assigned VLAN
• Include FHRP group name on interface lists
• Add 802.1Q mode to interface filter form
• Show count of related VLAN groups under cluster view
• Add "copy to clipboard" button for rendered config
• Enable filtering devices by location slug
• Add filtering by VLAN translation policy to interface filter forms

Bug Fixes:

• prepare_cloned_fields() should validate cloning support on model
• Ensure default custom field values are respected when creating objects via the REST API
• Include missing related object counts under certain views
• Omit "clear" button on required choice fields
• Preserve ordering of terminations in cable traces
• Virtual chassis form should exclude members of other VCs when adding members
• Fix custom field choices bulk import support for base_choices
• The load_yaml() convenience method on BaseScript should use SafeLoader
• Language cookie should respect SESSION_COOKIE_SECURE value
• Allow label reuse when creating multiple components from a pattern
• Restore editing conflict protection for several object forms

https://github.com/netbox-community/netbox/releases/tag/v4.2.8

MFH: 2025Q2
(cherry picked from commit 3a7416abae7df0c688ff2fa7da137d58aaecd3b1)