Add @classmethod get and from_dir

from dataclasses import dataclass

from pathlib import Path

from typing import Self

from collections.abc import Iterable, Iterator

from pathlib import Path

from ..integration.schwalbe.studienfachschaften import Studienfachschaft

from ..utils import group_by

from .PaymentOrder import PaymentOrder

    base_dir: Path

    @classmethod

    def get(cls, studienfachschaft: Studienfachschaft, year: int) -> Self:

        pass  # TODO

    @classmethod

    def from_dir(cls, path_or_str: Path | str) -> Self:

        pass  # TODO

    def __iter__(self) -> Iterator[PaymentOrder]:

        return (load_pdf(pdf) for pdf in self.base_dir.rglob("*.pdf"))