Definitions for enums in a vector are not generated

[zedkipp]

Hi @glaceef, Thanks for creating this helpful crate.

I am having an issue where enums with the #[rschema(defs)] attribute inside a Vector are not added to the generated schema definitions. The generated array schema refers to the definition, but the definition itself is not generated.

I've modified an existing test to demonstrate this issue here: zedkipp@9471a5d

If the enum is used anywhere else in the schema structure(s), the enum definition seems to be correctly generated.