doesn't use an enabled hasher.
Regression in aeb1389442d0f9669edf6660b747fd10693b63a7.
Reverted changes to is_password_usable() from
703c266682be39f7153498ad0d8031231f12ee79 and documentation changes from
92f48680dbd2e02f2b33f6ad0e35b7d337889fb2.
The previous version of Argon2 uses encoded hashes of the form:
$argon2d$m=8,t=1,p=1$<salt>$<data>
The new version of Argon2 adds its version into the hash:
$argon2d$v=19$m=8,t=1,p=1$<salt>$<data>
This lets Django handle both version properly.