Register under custom keys (and alias)

[AMHOL]

I think it would be good to allow types to be registered under custom keys, this way we can register under symbol keys and reduce allocations. Would also be good to allow for aliases (i.e. :int => :integer, :bool => :boolean). This should also allow us to get rid of the const_missing definition and I think the interface will be nicer.

Also, perhaps we should move the registration out of Dry::Data::Struct and make it explicit (i.e. Dry::Data.register(:name, Type, aliases: [:alias1, :alias2]).

This should make the library much more flexible, the obvious detriment is that there will be a bit of setup involved. I think it would also be good to make it so that a user can get a container without any of the built in types, and just create Dry::Data container and register the built-in types.

[AMHOL]

@solnic has already done this ❤️

[solnic]

I guess I did :) but what about aliasing? you think it could be a useful feature? I'm having doubts

[AMHOL]

Nah, there's more than one way to skin a cat, but there probably shouldn't be.

I was just thinking str vs string and int vs integer etc.