Enum concept

[vinipsmaker]

Boost.Hana currently has Struct. I have some code that performs automatic serialization for Struct types. However an Enum is missing in Boost.Hana to help here further.

The Struct concept [...] it allows accessing the names of the members of a user-defined type, and also the value of those members

For the Enum concept, I'd expect a similar mapping, however values should be hana::int_c<something> (non-mutable).