Part Two: Authentication and access control system You are to implement a simple "file system" with login authentication and access control. Specifically: Construct a hash$/$salt$/$shadow based user$/$password creation system. Construct a hash$/$salt$/$shadow based user authentication system. Construct an associated file system, into which a user can log$.$ Files can be created, read from, written to$,$ but only in accordance with a four$-$level access control model. The levels of the four$-$level access control model are $0,1,2$ and $3\mathrm{.}0$ is dominated by $1,2$ and $3$ ; and $1$ and $2$ are dominated by $3$ ; and $1$ is dominated by $2.$ Remark: You do not need to have an actual file system, simply an internal collection of records at the levels specified. You can implement the program in C$++$