Support vars whose type is nested e.g. var someVar: Nested.Name

[entonio]

Currently, if there are members whose type is a nested type, they will be ignored by the decoder code generator (not by the CodingKeys nor by the encoder), e.g. :

var carrotId: Fruit.Id

will have a corrresponding CodingKey, will be present in the encoder body, but skipped by the decoder.

I think it requires support in SimpleCodableMacro.swift:59-93, but I'm not sure what needs to be done.