[DEV] Entity states

[gdassori]

An entity must be allowed to enter a particular state that overrides the default commands observer.

Basic Implementation:

• Quit (yes/no)

[gdassori]

The entry point could be the WorkerQueueService which have to expose a

add_observer_per_entity(entity_id: int, observer: ObserverClass)

method that overrides the default commans observer.

[gdassori]

The current character state must be saved on Redis, since any worker must be able to see it.

[gdassori]

The states index must be generic, since also an item could be in a particular state.
For example a cursed item that can't be picked up for a while.

If no state is set for an entity, a default must be used.