fix: Root user password assignment in MySQL and MariaDB

[k3yss]

This PR addresses an issue in MySQL or MariaDB where attempts to assign a password to the root user are unsuccessful, resulting in the default blank password being used.

Fixes #1251

[domenkozar]

@YSawc can you try this branch?

[YSawc]

@domenkozar
I'm new comer of devenv project, so my confirmation way may not right but, after checkout this branch and build after comnad of direnv allow ., it seems resolved root password bug. Is this right way? If it's so, this PR looks no probrem.

[k3yss]

@YSawc Did you do this https://devenv.sh/community/contributing/

[YSawc]

@YSawc Did you do this https://devenv.sh/community/contributing/

I just done it and after devenv up below devenv.nix, mysql password applied root user. Thanks your fix.

...
  services.mysql = {
    ..
    ensureUsers = [
      {
        name = "root";
        password = "[PASSWORD]";
        ...
      }
    ];
  };

[JoeDupuis]

This breaks trying to create a user without a password: #1443

Setting an empty password is a workaround, but we should support the default value (null) without crashing.