dev.knotless.assignment

Kept in the account of the owner or collaborator who assigns, one per pull or issue, keyed `<repo key>.<hash of the subject's URI>` as a dev.knotless.label record is, and rewritten as they change; for a private repository, in their repo inside its space. Readers honor it from the repository's owner and collaborators alone. Each account stands assigned, or asked to review, as the latest of their entries for it says, by `setAt`. A pull's author asks for reviews in the pull itself (dev.knotless.pull's `reviewers`); those asked here are asked besides.