Ft: multi-user auth, user model, files and pages owned by username

[binizikrr]

Multi-user auth and content ownership. Fork based on tag version 0.3.4-0.3.5

[gribanoveu]

Hi, codex-team, can you look at this code? 👉👈

@neSpecc, @gohabereg, @n0str, @PolinaShneider