lib/types/string.ex
defmodule DryValidation.Types.String do
@moduledoc """
Represents a string type.
```
DryValidation.schema do
required :name, Types.String
end
```
"""
@doc false
def cast(value), do: value
@doc false
def valid?(value) when is_binary(value), do: true
def valid?(_value), do: false
end