Ensure proper code coverage with additional validation and preconditions

[BrendonButler]

When sending commands, it appears that autocomplete wont work for console users -- warning that they are not a player. But they can still enter and attempt to submit these commands.

In this case, the resulting error should be handled more gracefully than printing a stack-trace. Some commands should also have console functionality. Such as adding items to a shop or removing items from a shop.

[BrendonButler]

I would like to expand this issue to cover all additional validation that needs to be done.

This would include ensuring each command has proper coverage and preconditions to prevent unhandled errors. I would also like to investigate any potential issues or additional checks in the InventoryManagementSystem and other utilities.

[BrendonButler]

This will continually improve over time, and I will be fixating on validation and preconditions for all new code that I implement. The code is in a much better state now to continue working on new features without existing bugs causing hiccups.