Add Vue 3 rollout metadata for seat management pages

What does this MR do and why?

Moves the 24 page entrypoints owned by group::seat management to Vue 3, behind our own feature flag vue3_migrate_seat_management. The flag is off by default, so there is no change in production until we enable it.

The repo-wide final sweep (!261154 (merged)) merged with these entrypoints excluded, so they are currently still on Vue 2. An own flag gives us a rollback lever scoped to our pages instead of one shared with every other laggard.

Each entrypoint gets a vue3_migration.yml next to its index.js. admin/users and admin/users/edit exist in both CE and EE, so they get two identical copies, as the loader requires. That is 26 yml files for 24 entry names, plus the flag definition.

status: rollout
feature_flag: vue3_migrate_seat_management
group: group::seat management
migration_issue: https://gitlab.com/gitlab-org/gitlab/-/work_items/633485

Ownership comes from the Vue 3 migration dashboard (https://vue3-migration-dashboard-0afc95.gitlab.io/), which attributes an entrypoint by its controller's feature_category. .gitlab/CODEOWNERS is not usable for this: it has no app/assets rules for Fulfillment, so every path falls through to the frontend maintainers catch-all.

Screenshots or screen recordings

No UI change while the flag is off.

How to set up and validate locally

1. Enable the flag: Feature.enable(:vue3_migrate_seat_management).
2. Restart vite, then open one of the pages below.
3. Confirm the page requests <entry>.vue3.js and that the console logs [V] Using Vue.js 3 for <AppName>.

Verification

All 24 entrypoints were loaded in a browser with the flag on, against an Ultimate licence. Every page served its .vue3.js entrypoint, mounted its app under @vue/compat, and logged no console errors.

#	Entrypoint	URL	Apps mounted under Vue 3
1	pages.admin.application_settings.roles_and_permissions	/admin/application_settings/roles_and_permissions	RolesRoot
2	…roles_and_permissions.new	…/roles_and_permissions/new	CreateRoleRoot
3	…roles_and_permissions.show	…/roles_and_permissions/:id	RoleDetailsRoot
4	…roles_and_permissions.edit	…/roles_and_permissions/:id/edit	EditRoleRoot
5	pages.groups.settings.roles_and_permissions	/groups/:g/-/settings/roles_and_permissions	RolesRoot
6	…roles_and_permissions.new	…/roles_and_permissions/new	CreateRoleRoot
7	…roles_and_permissions.show	…/roles_and_permissions/:id	RoleDetailsRoot
8	…roles_and_permissions.edit	…/roles_and_permissions/:id/edit	EditRoleRoot
9	pages.admin.application_settings.service_accounts	/admin/application_settings/service_accounts	ServiceAccountsRoot, CustomBreadcrumbsRoot
10	pages.groups.settings.service_accounts.index	/groups/:g/-/settings/service_accounts	ServiceAccountsRoot, CustomBreadcrumbsRoot
11	pages.projects.settings.service_accounts.index	/:g/:p/-/settings/service_accounts	ServiceAccountsRoot, CustomBreadcrumbsRoot
12	pages.admin.users	/admin/users	AdminUsersAppRoot, AdminUsersFilterAppRoot, DeleteUserModalRoot, ConfirmModalRoot
13	pages.admin.users.edit	/admin/users/:user/edit	PasswordInputRoot, UserTypeSelectorRoot, ResetButtonRoot
14	pages.admin.users.new	/admin/users/new	UserTypeSelectorRoot
15	pages.admin.credentials	/admin/credentials	CredentialsFilterSortAppRoot
16	pages.admin.impersonation_tokens	/admin/users/:user/impersonation_tokens	AccessTokenTableRoot, ExpiresAtFieldRoot, NewAccessTokenRoot, AdminUserActionsRoot
17	pages.admin.keys	/admin/users/:user/keys/:id	ConfirmModalRoot
18	pages.admin.role_promotion_requests	/admin/role_promotion_requests	PromotionRequestsAppWrapper
19	pages.admin.gitlab_duo.seat_utilization	/admin/gitlab_duo/seat_utilization	CodeSuggestionsUsage
20	pages.groups.ldap_group_links	/groups/:g/-/ldap_group_links	GroupLinkRoleSelectorRoot, GroupSelectRoot
21	pages.groups.saml_group_links	/groups/:g/-/saml_group_links	GroupLinkRoleSelectorRoot
22	pages.groups.security.credentials	/groups/:g/-/security/credentials	CredentialsFilterSortAppRoot, ConfirmModalRoot
23	pages.groups.usage_quotas.pending_members	/groups/:g/-/usage_quotas/pending_members	PendingMembersAppRoot
24	pages.users.terms.index	/-/users/terms	TermsAppRoot

Rows 1-4, 15, 18, 19 and 20 are self-managed only and were checked with GITLAB_SIMULATE_SAAS=0; rows 5-8, 21, 22 and 23 need SaaS mode and were checked with GITLAB_SIMULATE_SAAS=1.

Beyond page load, the create-role form was submitted end to end on both row 2 and row 6: the base-role dropdown, the permission checkboxes and the submit all behaved correctly under Vue 3, and the created role then rendered on the show and edit pages.

The one non-Vue console error seen, and why it is unrelated

On /admin/gitlab_duo/seat_utilization the page logs an Apollo error. The only failing request is POST /-/customers_dot/proxy/graphql returning 404, so the proxy returns an HTML error page where Apollo expects JSON. The page itself mounts CodeSuggestionsUsage and renders.

This is not reachable locally for this page, with or without CustomersDot running:

• CustomersDot::ProxyController renders 404 unless Gitlab::Saas.feature_available?(:cdot_graphql_proxy), which is just Gitlab::Saas.enabled? (ee/lib/gitlab/saas.rb:67), so it needs SaaS mode.
• Admin::GitlabDuo::SeatUtilizationController renders 404 unless !gitlab_com_subscription?, so the page needs self-managed mode.

The two conditions are mutually exclusive on one instance, so the proxy can never answer for this page locally. Starting CustomersDot on localhost:5000 does not change the result.

It is also independent of this MR: with vue3_migrate_seat_management disabled, the same page loads the Vue 2 bundles and produces the identical 404 and the identical Apollo error.

Why data-gitlab-vue3-app is not the signal used here

doc/development/fe_guide/vue3_migration.md suggests checking document.querySelectorAll('[data-gitlab-vue3-app]'). That attribute is only stamped when an app is constructed through the compat wrapper with an el option (app/assets/javascripts/lib/utils/vue3compat/vue.js:55 and mount_wrapper.js:44). Pages whose apps mount another way return nothing even though they do run under Vue 3 — the roles show page is one such case. The checks above therefore use the loaded <entry>.vue3.js bundle plus the [V] Using Vue.js 3 for <AppName> dev notice, which hold for every mount path.

Automated checks:

• node -e 'require("./config/vue3migration/migration.js").loadVue3Migrations()' resolves all 24 entry names, with no CE/EE divergence.
• spec/lib/gitlab/vue3_migration_files_spec.rb — 3221 examples, 0 failures.

MR acceptance checklist

Evaluate this MR against the MR acceptance checklist.

References

• Rollout issue: #633485
• Final sweep MR that excluded these entrypoints: !261154 (merged)
• Vue 3 migration epic: &23285