Argon2PasswordHasher.verify() should be agnostic to the algorithm version

[Till Kolter]

Hi,

I have two seperate sources capable of generating user passwords (one is a legacy system but unfortunately it will not go away for a while). 

The legacy system uses Argon2id while the new Django-based system is fixed to version Argon2i for both encoding and decoding.

In my opinion the decoding `verify` function should be agnostic to the version of the algorithm and set the type on the part of the string like:

```
def verify(self, password, encoded):
   argon2 =3D self._load_library()
   algorithm, rest =3D encoded.split('$', 1)
   assert algorithm =3D=3D self.algorithm
   alg_identifier, _ =3D rest.split('$', 1)
   alg_short =3D alg_identifier.split('argon2')[1]
   type =3D getattr(argon2.low_level.Type, alg_short.upper())
   try:
       return argon2.low_level.verify_secret(
           force_bytes('$' + rest),
           force_bytes(password),
           type=3Dtype,
       )
   except argon2.exceptions.VerificationError:
       return False
```

What do you think?

Till