Link Buy Command to Wallet

[Raikonen]

• Update the Wallet accordingly when Buy Command is executed
• Add Exception Handling when Wallet has insufficient funds
• Add a cap to price of food item, i.e. maximum of $5000.00

[jon-chua]

Issue found when testing, may be due to parsing of doubles.

Steps to reproduce:

1. budget 10000 2
2. add n/Mala Xiang Guo p/0.01 d/Spicy goodness c/Chinese t/Spicy t/Healthy l/University Town o/0800 2000 r/Vegetarian
3. buy 7 (or whatever that item was) 4 times

The wallet updates to 9999.99, then 9999.98, 9999.97 and then 9999.95 🤔

Other than that issue, lgtm 👍

[Raikonen]

Okay, fix for this issue will be in the next PR

Issue found when testing, may be due to parsing of doubles.

Steps to reproduce:

1. budget 10000 2
2. add n/Mala Xiang Guo p/0.01 d/Spicy goodness c/Chinese t/Spicy t/Healthy l/University Town o/0800 2000 r/Vegetarian
3. buy 7 (or whatever that item was) 4 times

The wallet updates to 9999.99, then 9999.98, 9999.97 and then 9999.95 🤔

Other than that issue, lgtm 👍

[jon-chua]

LGTM, remember to fix the issue above 👍