Support nested conditional fields

[shahryarjb]

You may have reached this issue by searching. I spent three weeks full time trying to implement this possibility. But unfortunately I did not succeed. If you have an idea to implement this possibility in this macro, please cooperate.

  guardedstruct do
    conditional_field(:actor, any()) do
      field(:actor, struct(), struct: Actor, derive: "validate(map, not_empty)")

      conditional_field(:actor, any(),
        structs: true,
        derive: "validate(list, not_empty, not_flatten_empty_item)"
      ) do
        field(:actor, struct(), struct: Actor, derive: "validate(map, not_empty)")

        field(:actor, String.t(), derive: "sanitize(tag=strip_tags) validate(url, max_len=160)")
      end

      field(:actor, String.t(), derive: "sanitize(tag=strip_tags) validate(url, max_len=160)")
    end
  end

Branch link:
https://github.com/mishka-group/mishka_developer_tools/tree/nested_condition