API errors: merged all `unknown-*` error ids into either `unknown-resource` or `unknown-referenced-resource` (with consistent `error.data`)
API errors: merged `item-*-already-exists` error ids into `item-already-exists` (with consistent and informative `error.data`)
API errors: `missing-parameter` replaced with `invalid-parameters-format`, `register-invalid-authentication` with `unknown-resource` (user creation from reg server)
Added API change log & FAQ pages & fixed text content width for text-only pages
Quick tweaks
Added raw auth flow to reference, removing links to "auth" page