Aligns the InferenceBackend ownership column with the principal-based
ownership model used elsewhere (clusters, model_routes). NULL identifies
platform-curated rows shared across orgs; a populated value identifies
an org-scoped override or custom backend.
Four purely-additive seams that let build-time tooling extend host
behaviour without forking files:
* `src/access.extensions.ts` — identity `applyAccessExtensions`
(mirrors `config/routes.extensions.ts`). `src/access.ts` runs the
resolved predicate object through it. Adds two new predicates,
`canSeeOrgAdmin` and `canManageCurrentOrg`, alongside the existing
`canSeeAdmin`. Resources, Models children, Cluster Management, and
Resources/Backends are retagged from `canSeeAdmin` to
`canSeeOrgAdmin`. Users and Dashboard stay strict.
* `src/request.extensions.ts` — identity-empty
`extraRequestInterceptors`. `src/request-config.tsx` spreads it
into the existing `requestInterceptors` list so extensions can
inject context-aware headers without forking the request config.
* Users page action column — renders
`getGPUStackPlugin()?.components?.UserRowActions` next to the
existing DropdownButtons inside a Space when a plugin component
is registered. If absent, the cell renders exactly as before.
* `src/components/plugin-extra-fields.tsx` — generic component-slot
helper. Renders `pluginManager.components.<name>` if registered,
forwarding a `context` payload. Used by create/edit forms to let
plugins inject extra `Form.Item` fields. Mounted in the relevant
create forms — API Keys, Cloud Credentials, Clusters, Model
Routes, Model Providers, and Inference Backends — under the slot
name `CreateOrgScopeField`. Resources whose org is implicit from a
parent (Models / Workers / Benchmarks / Worker Pools / Model Files
inherit from the chosen Cluster) deliberately don't mount the slot.
