@spec constraints(any(), Keyword.t()) :: Validate.error_map()

I traverse a given data structure and return the values that are nil or invalid according to their protocol.

For any value that is not enumerable, I return no errors.

Note: we assume that there are no missing keys, otherwise the GRPC request would fail anyway. So it's only necessary to check for existing keys that are nil.

@spec validate(any(), Keyword.t()) ::
  {:ok, :valid} | {:error, :invalid, Validate.error_map()}

Validates a value with the given options.

This function will call the constraints function on the value and translate that result into a result.