Require at least one auth from a set of auths

Question

require_auth() asserts that a particular auth is present.

How to write a contract that proceeds if and only if at least one of a set of auths is present?

Answer 1

eosio_assert(
  has_auth(accounta) || has_auth(accountb),
  "missing required authority of accounta or accountb");

See: https://eosio.github.io/eosio.cdt/1.5.0/group__action.html#function-hasauth