Use of password hash with insufficient computational effort

[okawaffles]

Tracking issue for:

• [ ] https://github.com/okawaffles/OkayuCDN/security/code-scanning/100

will change the method of password hashing method later.

plan of attack for older accounts:

1. user has signed up with sha256 hash
2. on next login, if userdata uses sha256 hash, re-hash password and save new userdata
3. save config with marker that can differentiate sha256 from argon2d or whatever

[okawaffles]

Passwords are re-hashed with argon2 on login if the user created their account with a sha256 hash. Signup POST needs changing but everything else should be good.