Complex types for command line arguments and environment variables

[silvanmelchior]

By their nature, command line arguments and environment variables only support strings. Pydantic then casts them to other primitives, e.g. an integer. However, it is not possible to far to define more complex types, e.g. a list or a dictionary. It would be interesting to support this as well.

Whereas lists for command line arguments could be realised by passing the same argument multiple times with potentially different values, it is not clear how this would work for environment variables and how other types like dicts would be realised. One possibility would be a special encoding (e.g. json), but this would then have to be parsed explicitly by confz before calling pydantic.