Invalid state should raise some specific exception

[kiblik1]

method is rising without obvious cause leading to weird behavior such as #14

https://github.com/anitabyte/etsyv3/blob/8af196816ed64e8bc62a9adfb7f035999ec96fb7/etsyv3/util/auth/auth_helper.py#L46C8-L46C8

Should raise something more helpfull e.g. ValueError("Invalid state")