[SAK-FEA-4] Create an auth system

[anafro]

Issue information

• Sakurator last version when issue was suggested: 1.0.0.2
• Type: feature (important)

Why this feature should be added?

Now statistics are saved in cookies. So this is both convenient and inconvenient at the same time. It would be cool to implement the auth system - this will help to save, update and restore the progress of learning the hiragana and katakana.

An enhancement unside the enhancement

Maybe to create one universal auth gate for it? Like 'Anafro ID' or something? It sounds crazy for me, but if I implement this, it'll open a big world for me - like subscription systems, global notifications and much-much more

Difficulty for me

So, it is a challenging one. I didn't implement the auth system from scratch. Maybe there is some simpler and safer solution for that?

Probable issues

So, many things can happen, but I can't predict yet