-`recruit`, which adds a member to the members vector of the Mob when receiving a `member_name` (&str) and a `member_age` (u8) (the role should be Associate)
-`attack`, which receives another Mob and will remove the last member from the vector of Members from the Mob with the less power combat (in case of draw, the loser is the attacker). The power combat is calculated by its members:
- In case of one of the mobs stays without members, the winner mob adds to its cities every city of the loser mob and the same happens to the wealth, and the loser mob loses all cities and all wealth
-`steal`, which receives a targeted mob (Mob) and a value (u32) and subtracts the value from the target mob. The value is then added to itself. It can't be stolen more than the target mob currently has.
-`conquer_city`, which receives a vector of mobs, a city name (String) and a value (u8) and adds it to the vector of cities of the own mob, only if no mob in the vector owns a city with this name
- the Member struct should implement a function `get_promotion` which will change the member role. If a member is an Associate, it will get promoted to Soldier; a Soldier is promoted to a Caporegime and a Caporegime is promoted to Underboss