ParseAuthLevel parses authentication level from a string.

LevelAnon is anonymous user/light authentication.

LevelAuth is fully authenticated user.

LevelNone is undefined/not authenticated.

LevelRoot is a superuser (currently unused).

Validated bit is set if user's credentials are already validated.

Rec is an authentication record.

AuthHandler is the interface which auth providers must implement.

Feature is a bitmap of authenticated features, such as validated/not validated.

Level is the type for authentication levels.