Guard a read model with the authorization of the queries that read it - #29

The attribution key

A query names the read model it reads with its return type, so Identifiers.ToPascalCase(query.ReturnType.Name) against the projection's read model name is the key. IsCollection is ignored — InvoiceListReadModel[] reads InvoiceListReadModel just as a single instance does. The invoicing sample's slice StateView InvoiceDashboard is exactly this shape: one projection building InvoiceSummaryReadModel, plus a GetOverdueInvoices => OverdueInvoicesReadModel[] query for a read model the slice never projects.

Why the unqueried read model does not simply render anonymous

Filtering alone would have introduced a new permissive path: a read model whose slice declares queries only for its siblings would go from a (wrong, but closed) foreign guard straight to [AllowAnonymous]. So the no-own-queries case falls back to Authorize plus a diagnostic — the same fallback AuthorizationRenderer already uses for an undeclared policy, a code policy and a claim policy. The two silences are deliberately distinguished: a slice declaring no query at all says nothing about reading anything and keeps its existing [AllowAnonymous]; a slice that states read authorization for its other read models and none for this one is a document whose silence must not be read as a grant.

The pre-existing "a read model with no declared queries anywhere still gets an unguarded all/by-id pair the document never asked for" is untouched and out of scope here.

Not this PR

#20 (authorize A B rendering as Roles(A, B)) is independent and untouched, as is its deliberately-wrong pinning spec and_one_of_several_declarations_is_missing. That collapse is correct within one read model — and_one_of_its_own_queries_is_unguarded pins it staying that way.

Verification

• dotnet build -c Debug and -c Release — 6 projects, 0 errors, 0 warnings.
• dotnet test — 367 passed, 0 failed (Contracts 125, Stage 19, Rendering.Cratis 223; 10 of those new).
• dotnet pack -c Release — exit 0, 0 warnings, package validation clean against the 2.0.0 baseline. ReadModelAuthorization is additive public API, which is the second reason for minor beside the rendering-behavior change.
• Red proof: reverting only the call site in StateViewSliceRenderer to the whole-slice union fails when_another_read_model_has_an_unguarded_query on both assertions — [Roles("Accountant")] not found, [AllowAnonymous] present — while should_render_the_first_projections_read_model still passes, so the failure is specific to authorization rather than the fixture.