Fix: update Product.item components

[madcalf]

Updates the Product.info components' field names to be more consistent and/or clarify their intent.
Also removes the default values in the weight component.

Closes #63

[jtfairbank]

• Praise: Great job touching up all of the documented consistency issues!
• Suggestion (blocking): Noticed a few others while I was reviewing. Can we address them in this PR too?
  • for item.needsMet, rename monthlyNeedsMetPerUnit to monthlyNeedsMetPerItem so that we're using the item / unit terminology consistently
  • for item.value make the source and logDate fields required, to be consistent with item.volume and item.weight
• Question: For item.value, do you think it'd be worth adding a packagePriceUnit field, set to USD as a constant for now? And what about naming itemPrice to itemPriceUSD for consistency with itemVolume and itemWeight which include units in the field name?

[jtfairbank]

@madcalf testing 123

[madcalf]

rename monthlyNeedsMetPerUnit to monthlyNeedsMetPerItem so that we're using the item / unit terminology consistently

Rename is done. Will make monthlyNeedsMetPerItem a calculated field in a separate PR.

[madcalf]

For item.value, do you think it'd be worth adding a packagePriceUnit field, set to USD as a constant for now?

Sure that makes sense. Added it as an enum with USD as the default (and currently the only) option, and we can add in additional currency values needed.

[madcalf]

And what about naming itemPrice to itemPriceUSD for consistency with itemVolume and itemWeight which include units in the field name?

Renamed itemPrice to pricePerItemUSD because i kept getting it confused with the packagePrice and it seems more in line with the other calculated field names. I'll also make this one a calculated field in a separate PR.

[jtfairbank]

@madcalf looks great!