query minted token address on starknet using static keys

[rnbguy]

hermes-sdk has derive_ibc_denom to find the ibc minted denoms (of the form ibc/<hash>) in cosmos-sdk based chains. This is a pure function as <hash> can be derived statically from trace prefix and native denom.

But in starknet, the tokens are minted by deploying a new erc20 contract. So the minted token denoms (contract addresses) can't be derived statically. The ics20 contract maintains a map of keys (which can be statically derived) of the minted token and the corresponding token addresses.

ibc-starknet/cairo-contracts/packages/apps/src/transfer/components/transfer.cairo

Lines 34 to 39 in 717b229

	pub struct Storage {
	erc20_class_hash: ClassHash,
	salt: felt252,
	ibc_token_key_to_address: Map<felt252, ContractAddress>,
	ibc_token_address_to_key: Map<ContractAddress, felt252>,
	}

Thus, StarknetChain needs a method which takes the same arguments as derive_ibc_denom and derive the key (using poseidon hash) and query the ics20 contract for the token address.

ibc-starknet/cairo-contracts/packages/apps/src/transfer/components/transfer.cairo

Lines 777 to 781 in 717b229

	let denom_key = denom.key();
	self.write_ibc_token_key_to_address(denom_key, token_address);
	self.write_ibc_token_address_to_key(token_address, denom_key);

ibc-starknet/cairo-contracts/packages/apps/src/transfer/components/transfer.cairo

Lines 276 to 284 in 717b229

	fn ibc_token_address(
	self: @ComponentState<TContractState>, token_key: felt252
	) -> ContractAddress {
	let address = self.read_ibc_token_address(token_key);
	assert(address.is_non_zero(), TransferErrors::ZERO_TOKEN_ADDRESS);
	address
	}

[rnbguy]

Once this is done, we can remove the ibc_token_addresses endpoint from the ics20 cairo contract

ibc-starknet/cairo-contracts/packages/apps/src/transfer/components/transfer.cairo

Lines 287 to 289 in c13b888

	fn ibc_token_addresses(self: @ComponentState<TContractState>) -> Array<ContractAddress> {
	self.read_ibc_token_addresses()
	}

and stop maintaining the all token addresses:

ibc-starknet/cairo-contracts/packages/apps/src/transfer/components/transfer.cairo

Line 39 in c13b888

token_addresses: Vec<ContractAddress>,