MishkaCmsCore.Runtime.Resources.Validations.AnchorSiteRequired (Mishka CMS Core v0.0.1)

A page and an error page are never global; a layout and a component can be.

MishkaCmsCore.Runtime.PageBuilderEvent anchors to all four through one polymorphic source_type, so it is global? true — a component's history has to be writable with a nil site_id. That makes the resource unable to say, by its multitenancy alone, the thing that is nonetheless true of half its rows:

source_type in [:page, :error_page]  ⟹  site_id is present

Verified against the resources themselves rather than assumed: Page and ErrorPage declare global? false, Layout and Component declare global? true.

Paired with a check constraint of the same name on the table. This catches the bug with a message; the constraint catches the code path that skipped the validation — worth having both, because these rows are written from the editor's hot path by batched, retried upserts, which is exactly the sort of path that grows a shortcut.