Migrate waterfall allowed_vfolder_hosts merge to myStorageHostPermissions (Strawberry V2)

[agatha197]

Summary

Migrate the existing client-side allowed_vfolder_hosts merge ("which storage hosts can the current user mount") from the legacy request-waterfall pattern onto the myStorageHostPermissions GraphQL field (Strawberry V2, added in 26.4.2).

Background

The legacy pattern resolves the keypair's resource-policy name first, then issues a second query for domain / group / keypair_resource_policy allowed_vfolder_hosts, then merges three JSON blobs client-side and filters by mount-in-session. This is a request waterfall plus duplicated merge logic.

myStorageHostPermissions returns the union of domain + the user's projects + keypair permissions in a single server-side query, already intersected with registered volumes. FR-1436 introduced the useMountableVFolderHosts hook on top of it for the deployment model-folder selector; this issue generalizes that adoption.

Candidate consumers (Pattern A — "current user's mountable hosts")

• react/src/components/VFolderTable.tsx (session mount picker; inline VFolderTableProjectQuery + _.merge + mount-in-session)
• react/src/hooks/useMergedAllowedStorageHostPermission.ts and its consumers:
  • FileBrowserButton.tsx, FileBrowserButtonV2.tsx
  • FolderExplorerModal.tsx, FolderExplorerModalV2.tsx
  • SFTPServerButton.tsx, SFTPServerButtonV2.tsx

Explicitly OUT of scope (Pattern B — admin entity config)

Code that reads/writes a specific entity's allowed_vfolder_hosts (admin settings) must NOT be migrated — it is not "the current user's union": BAIProjectSettingModal, BAIProjectTable, KeypairResourcePolicy*, DomainStoragePermissionTable, ProjectStoragePermissionTable, helper/storageHostPermission.ts, BAIAllowedVfolderHostsWithPermission.

Key open decision — version floor

myStorageHostPermissions requires manager >= 26.4.2. Unlike the deployment modal (already gated >= 26.4.3), the Pattern A flows above (session mount, file browser, SFTP) currently support older managers and are NOT version-gated. Migrating them requires either:

• (a) keeping a fallback to the legacy merge for managers < 26.4.2 (keeps both code paths), or
• (b) declaring 26.4.2 the minimum supported manager and deleting the legacy path.

Decide the support matrix before implementing.

Acceptance criteria

• Pattern A consumers compute mountable hosts via myStorageHostPermissions (directly or by reimplementing useMergedAllowedStorageHostPermission internals while preserving its return shape).
• No behavioral regression for the chosen support floor.
• scripts/verify.sh passes.

Notes

• Stacked on top of the FR-1436 branch / PR feat(FR-1436): limit deployment model folder selector to mountable hosts #8083.
• host is server-side filterable on vfolder_nodes; selectors can compose host clauses into their GraphQL filter string (see FR-1436).

JIRA Issue: FR-3229