Satisfied when T has reflected members.
Declared in <mrdocs/Support/Describe.hpp>
template<class T>
concept described = has_describe_members<T>::value || has_describe_enumerators<T>::value;True for any type annotated with MRDOCS_DESCRIBE_STRUCT or MRDOCS_DESCRIBE_CLASS. Reads better than, and constrains templates on, has_describe_members<T>::value.