Escrow 721 setup

[humanalgorithm]

=> Setup working Escrow721 contract
=> setup e2e test in Go to load contracts and test all requisite functions
=> refactoring of e2etest so that we can test each function individually

As part of the ICS721 spec we need an Escrow contract that essentially acts as a container for NFTs. In this PR I am implementing the functions that are needed in an escrow contract. This escrow contract will be used by ICS721 to store NFTs at each connection. For example, if we open a connection between Stargaze and Omni, we would have one of these Escrow contracts instantiated for that channel connection.

Per the spec it should implement the following functions:

function SaveClass(
  classId: string,
  classUri: string) {
  // creates a new NFT Class identified by classId
}

function Mint(
  classId: string,
  tokenId: string,
  tokenUri: string,
  receiver: string) {
  // creates a new NFT identified by <classId,tokenId>
  // receiver becomes owner of the newly minted NFT
}

function Transfer(
  classId: string,
  tokenId: string,
  receiver: string) {
  // transfers the NFT identified by <classId,tokenId> to receiver
  // receiver becomes new owner of the NFT
}

function Burn(
  classId: string,
  tokenId: string) {
  // destroys the NFT identified by <classId,tokenId>
}

function GetOwner(
  classId: string,
  tokenId: string) {
  // returns current owner of the NFT identified by <classId,tokenId>
}

function GetNFT(
  classId: string,
  tokenId: string) {
  // returns NFT identified by <classId,tokenId>
}

function HasClass(classId: string) {
  // returns true if NFT Class identified by classId already exists;
  // returns false otherwise
}

function GetClass(classId: string) {
  // returns NFT Class identified by classId
}

[shanev]

It's preferable to use &str here than owned strings. Did you run into issues using &str?

[shanev]

Can you add a comment about what these strings represent?

[humanalgorithm]

Changed to <&str, String> with a comment

[mccallofthewild]

Add response attributes for indexers "action", "save_class", "class_id", class_id

[humanalgorithm]

Added these attributes

[mccallofthewild]

CW Standard: add query_ prefixes to differentiate query implementation functions.

• fn query_nft_info
• fn query_has_class
• fn query_get_class

[humanalgorithm]

@mccallofthewild per the IBC spec this should actually be called "GetNFT"
https://github.com/cosmos/ibc/pull/615/files#diff-254e967536211862be86cdfb12569fbcaa03eaf39672f9fae5ab7b226b57cc8fR152

I would like to stay with the spec names wherever possible
But on the other hand I think anytime a query is performed it would be through the query function so possibly it doesn't need to stay with the spec name

Let me know what you think (I changed it to GetNFT for now which is what I originally intended)

[mccallofthewild]

@humanalgorithm GetNFT sounds right.

It may be wise to make the functions public as well. The main purpose for the query naming convention is to make it easy to wrap/extend the contract without losing compatibility with the canonical codebase.

[humanalgorithm]

@mccallofthewild I'll make the query functions public

[humanalgorithm]

@mccallofthewild per the duplicate package comment:

This is just the appearance of a duplicate, but not an actual duplicate => let me explain.
So per this article: rust-lang/cargo#1462
When we are referring a Cargo package as a Github address, what we do is specify the Github link and then Cargo auto crawls the repo to find the desired subfolder

Note that the cw721-ibc repo actually has two packages in it, from the Cargo.toml file in cw721-ibc repo:

[profile.release.package.cw721-ibc]
codegen-units = 1
incremental = false

[profile.release.package.cw721-base-ibc]
codegen-units = 1
incremental = false

A note about Cargo packages:
Here it looks like a duplicate because you see the same Github address twice, however once we turn these folder into Cargo packages, the address for each package will actually be different despite the fact that they are part of the same Github repo

Note that I put out a call for someone to turn cw721-ibc into a Cargo package over on the ics721 working group channel.

[mccallofthewild]

@mccallofthewild per the duplicate package comment...

@humanalgorithm Gotcha. I deleted the comment when I realized it was pointing at a workspace. I'll take a look at cw721-ibc.