* We should use Argon2i, instead of Argon2d. Current implementation was
Argon2i and did not support d-one.
* Other Argon2i implementations on Go exists, but they implements not
the latest Argon2 1.3 version.
* Argon2 is not so trivial to rewrite from scratch.
* Used argon2 library contained testing-library import, that added -test
related flags to the command line.
* Argon2i has some cryptoanalysis, showing it is not so perfect as
expected.
So all the issues above are mitigated by replacing this hashing function
with much more simpler Balloon hashing written from scratch. Simplicity
wins.