Per-name update for SessionConfig.assetParameterMacros. A value or callback replaces the
macro; null marks it empty (parameters that use it are not sent); undefined removes the
customer macro so the macro table's unresolved or built-in fall-through behavior applies again.
Per-name update for SessionConfig.assetParameterMacros. A value or callback replaces the macro;
nullmarks it empty (parameters that use it are not sent);undefinedremoves the customer macro so the macro table's unresolved or built-in fall-through behavior applies again.