Feature/buy asset

[RomanCantu]

• Handle buy asset requests
• new update method for AssetRepos: update_owner
• add a message to justify the (un)successful BuyAssetRequest in BuyAssetResponse

[RobbieKiwi]

Maybe it would be clearer to have a method like "subtract money".
Also it is always better to use keyword arguments rather than positional arguments in case somebody changes the orders of arguments in future

[RobbieKiwi]

Generally speaking, a function that takes an object as an argument and does some operation should either:

• Return a new version of the object, leaving the original unchanged
• Return None and modify the original (A la inplace=True for dataframes)
  We should be clear about which one of these is happening. Usually the type hinting should make it clear.

In PlayerRepo._adjust_money I made a mistake by forgetting to add '.copy()' so it is BOTH mutating the object and returning a new object.

In Engine.handle_buy_asset_message, you should not be mutating the game_state object that is passed to the function.

The new game state should be generated something like this.
new_game_state = replace(game_state, players=players.subtract_money(x), assets=assets.change_owner(x))

Also note that for "players" and 'assets" we are also using the return-value, not expected a mutation of the original object

[RobbieKiwi]

Generally speaking, when you pass an argument to a function that acts on that argument either:

• It should return a new version of that object without changing the original copy (preferred option usually)
• Or it should change the object "in place" and return None
  And we should be quite explicit about which one of these is happening. Usually the function name and type hints make it clear enough.

If you look at PlayerRepo._adjust_money you can see an example of where I did this wrong, I forgot to add ".copy()" after the df so this function is BOTH mutating the original object and returning a new one.