private static <T> T getValue(Supplier<T> callable) {
        try {
            return callable.get();
        } catch (final Exception e) {
            throw new IllegalStateException("could not generate value for supplier: " + callable, e);
        }
    }
Determines whether all request headers are allowed.

@return true if all request headers are allowed,
        false if only specific request headers are allowed.
core/src/main/java/com/linecorp/armeria/server/cors/CorsPolicy.java