add a metadata view to designate an nft as a pack

[austinkline]

Closes: #149

Description

Some NFTs on Flow are Packs. They can be opened to obtain the contents inside of them, but are largely useless afterwards. Two examples of this are NFL All Day packs, and Gaia NFT Packs. In both of these cases, there isn't a standard metadata view to designate them as opened. Because of that, users are at risk of purchasing a pack they might not know is empty.

This view adds a way to detect if something is a pack, letting marketplaces decide what they should do with that information. Perhaps that just means displaying that the pack is opened, or it could mean disabling trading altogether.

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For contributor use:

• [ ] Targeted PR against master branch
• [ ] Linked to Github issue with discussion and accepted design OR link to spec that describes this work.
• [ ] Code follows the standards mentioned here.
• [ ] Updated relevant documentation
• [ ] Re-reviewed Files changed in the Github PR explorer
• [ ] Added appropriate labels

• [ ] Update the version in package.json when there is a change in the smart contracts

[bjartek]

+1

[austinkline]

Added a ticket so we can discuss: https://github.com/onflow/flow-nft/issues/149

[bjartek]

The semantics of packs is different in every implementation i have seen. Can we open up a bigger discussion around consumable/pack semantics?

I tried to create a tax reporting export to koinly and some packs/opening logic does not have enough data to cost-allocate the items in the pack/consumable to the new nfts. This is a pretty huge problem if the tax government comes calling.