feat(grc): remake of grc721 nft standard

[matijamarjanovic]

Modeling after grc20

This implementation is completely based on the exiting grc20 with adaptation to the concept of nft (taken from previos grc721 implementation). What I mean to say is, this code introduces the Teller system to the existing grc721. To maintain consistency I have also decided to keep the exact same godoc comments from the grc20 in places where applicable.

Regardless, grc20 may be lacking in some features regarding extensions (#3692) so I have decided to attemt to bypass them in this approach (this also removes the need for having additions like grc721_metadata etc.)

Hooks

Hooks (in context of token standards) are a concept that allows developers creating fungible and non fungible tokens to customize them to their own liking without having to have their own implementation of the token/nft. It encourages the use of the existing basic implementation, or rather Teller interface.
How it works: admin (meaning token creator) just defines a structure that is going to represent a hook which needs to implement a Hook interface (3 funcs):

• GetHookType() defining which token-native function is going to trigger the hook (mint, transfer, burn, etc)
• GetHookTime() defining the time of the triggering - before or after the native func
• last one being the hook itself so OnTransfer() or OnMint() ...

After creating a hook, token admin would just call the method RegisterHook() over the token (nft) instance which would add the hook to the token's hook registry and the hook would automatically be triggered on desired occasion.

Example (from hooks_test.gno):

type PausableHook struct {
	paused bool
}

func (h *PausableHook) GetHookType() HookType {
	return HookTransfer
}

func (h *PausableHook) GetHookTime() HookTime {
	return HookBefore
}

func (h *PausableHook) OnTransfer(nft *NFT, from, to std.Address, tid TokenID) error {
	if h.paused {
		return ufmt.Errorf("transfers are paused")
	}
	return nil
}

pausable := &PausableHook{paused: false}
nft.RegisterHook(pausable)

Batch operations

This implementation also adds a feature where batch operations are implemented such as BatchTransfer, BatchMint, BatchBurn, etc which are implemented through tellers as well. This contributes to easier usage of the nft realms and some gas efficiency.

[Gno2D2]

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[notJoon]

A - character is not allowed in the package name; thus, the CI has failed. You need to change it.

ref: https://go.dev/blog/package-names

[matijamarjanovic]

Thanks, this was fixed in 4ee51ca