feat(isbn): create isbn class

requirements.txt

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+attrs==23.1.0

src/bookstore/isbn.py

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+from attrs import define, field, validators
+
+
+# TODO: create checksum method
+@define(frozen=True)
+class ISBN(str):
+    number: str = field(converter=str, validator=validators.matches_re(r"^\d{10}$|^\d{13}$"))
+
+    def __str__(self):
+        if len(self.number) == 10:
+            return f"{self.number[:9]}-{self.number[9:]}"
+        return f"{self.number[:3]}-{self.number[3:4]}-{self.number[4:6]}-{self.number[6:12]}-{self.number[12:]}"