[Feature] Allowlisted minting of hypercerts

[bitbeckers]

Goal

Create a flow for distributing hypercerts with a predefined set of creators and claims

User stories

• As a coordinator, I want to be able to 'reserve' hypercerts for a given set of contributors
• As a developer, I want to be able to use the APP to create and store allowlists for hypercert minting
• As a user, I want to be able to find a reserved hypercert and claim it useing the app
• As a user, I want to be prompted in the app to claim allocated hypercerts

Technicals

Store allowlist

• Create array with arrays of value pairs: [[address, fraction],...]
• Generate Merkle root and proofs for arrays: https://github.com/OpenZeppelin/merkle-tree
• Call contract and store merkleRoot with totalUnits and URI to get claimID: https://github.com/Network-Goods/hypercerts-protocol/blob/dev/src/HypercertMinter.sol#L57
• Store tree and proofs in BE datastore in connection to claimID

Claim allowlist

• User provides wallet address
• User identifies claimID to mint
• BE queries datastore for proofs JSON related to claimID
• If found, provide proofs
• Send mint request with proofs to contract: https://github.com/Network-Goods/hypercerts-protocol/blob/dev/src/HypercertMinter.sol#L49

[bitbeckers]

Diverging from OZ because of: OpenZeppelin/merkle-tree#9