Prevent minting an NFT if it has already been minted in its current state

[drewcook]

Bug Notes

The NFT that represents the project in its given state should only exist once for the current version, or in 1155, there should only be one collection of that version. Currently, the user can mint an NFT from project C as it exists, say with two stems A and B. Another user can mint an NFT of project C with stems A and B as well. This ends up having two identical NFTs, just owned by different users. This should be prevented.

User Story

As a user, I should be able to mint a song into a token if there isn’t a token that exists with that exact combination of stems and collaborators. If a project has 3 stems on it and hasn’t been minted yet in that version, as a user, I should be able to mint that project. If a user comes along after me minting that project, and the project state hasn’t changed at all in the manner of new stems being added onto the project, then that second user should not be able to mint the project. In other words, there should only exist a version of an Arbor project at each state that the project has and no more than one per state.

“State” in this context means:

• The project with 2 stems from 1 collaborator
• The project with 3 stems from 2 collaborators
• The project with 4 stems from 2 collaborators
• The project with 5 stems from 3 collaborators
• etc.

A project could only have an NFT representing one of these states, nothing more, and no tokens with the same “configuration”, or “state”.

Expected Behavior

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Steps to Reproduce

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2. Click on '....'
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4. See error

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References

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OS & Device Information

Desktop (please complete the following information):

• OS: [e.g. iOS]
• Browser [e.g. chrome, safari]
• Version [e.g. 22]

Smartphone (please complete the following information):

• Device: [e.g. iPhone6]
• OS: [e.g. iOS8.1]
• Browser [e.g. stock browser, safari]
• Version [e.g. 22]

Additional context
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