Extract the redirect_uris array from a parsed RFC 7591 DCR request body,
returning an empty array when the field is absent or malformed. The number of
URIs collected is capped at maxRedirectUrisPerRegistration so an
unauthenticated POST /register carrying an oversized array cannot force an
unbounded allocation here before the proxy's own registration cap applies.
Extract the redirect_uris array from a parsed RFC 7591 DCR request body, returning an empty array when the field is absent or malformed. The number of URIs collected is capped at maxRedirectUrisPerRegistration so an unauthenticated POST /register carrying an oversized array cannot force an unbounded allocation here before the proxy's own registration cap applies.