Ability to categorize expenses per line item

What version of Invoice Ninja are you running? ie v4.5 / v5 v5.11.61 What environment are you running? Self-Hosted Have you searched existing issues/requests? No Additional context One of the most basic functions of accounting software is the ability to categorize each line item in an expense. The same goes for POs. I am a repair shop, and all my inventory is also sub-categorized based on type of part or a category that I can group them into. So if I buy 20 of x and 10 of y, x and y might not be the same style/category of part. Being able to track what types of parts I'm going through more is quite handy. Back to the main feature request. If I have an expense at a store, I might not be buying the same of one category. For instance, if I go to a gas station and get fuel, a candy bar, and a drink. The candy bar and drink can be expensed as meals and entertainment, while the fuel needs to go under vehicle expenses. Under the current versions, I can only categorize the en…