Defense-in-depth tenant isolation: every user-owned entity (Email, Sender,
MailThread, MailDomain, Attachment, Label, SyncState, AnalyticsAggregate,
WidgetLayout, UnsubscribeItem) gets a global query filter restricting reads to the
authenticated user. AppDbContext takes an optional ICurrentUser; CurrentUserId is
Guid.Empty for background workers / design-time, which DISABLES the filter so sync
and tooling (which already scope by an explicit userId) are unaffected. On the HTTP
attack surface a forgotten manual `WHERE UserId ==` can no longer leak another
tenant's rows.
Phase 1 confirmed no active IDOR; this is preventive, and prioritised now because the
upcoming automation engine will add many new queries.
Also: moved the Npgsql-only tsvector FTS mapping out of EmailConfiguration into
AppDbContext.OnModelCreating, guarded by Database.IsRelational() (Ignored otherwise),
so non-relational test providers work — honouring the existing Email.SearchVector
comment. Production (Npgsql) model is unchanged; no migration needed.
Adds 3 cross-user tenant-isolation integration tests. All 38 tests green.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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