LibraryDeskClient._resolve_user only enforced non-empty: an explicit
user argument to any tenant-scoped method bypassed tatlock's tenant
guard entirely and went straight to library-desk, and padded values
were sent un-stripped on the wire.
Route the explicit-arg path through the same apply_tenant_guard() used
by context resolution and strip whitespace before the empty check, so
a non-production environment can never send the production tenant (or
a sanitization-collision variant) to library-desk, regardless of how
the user was supplied. Defense in depth - no in-repo caller passes an
explicit user today.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
jpmschweitzerandClaude Fable 5
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