Export TermsOfService contract in Vault data structure (#199)

- Export `termsOfService` contract as the part of Vault data structure

eth_defi/enzyme/vault.py

@@ -109,6 +109,13 @@ class Vault:
     #:
     guard_contract: Optional[Contract] = None
 
+    #: Terms of service contract.
+    #:
+    #: - We must have a TermedVaultUSDCPaymentForwarder
+    #: - Resolved from TermedVaultUSDCPaymentForwarder.termsOfService() accessor
+    #:
+    terms_of_service_contract: Optional[Contract] = None
+
     #: What was the block number when this vault was deployed
     #:
     deployed_at_block: int | None = None
@@ -381,10 +388,14 @@ def fetch(
         else:
             generic_adapter_contract = None
 
+        terms_of_service_contract = None
         if payment_forwarder is not None:
             try:
                 payment_forwarder_contract = get_deployed_contract(web3, f"TermedVaultUSDCPaymentForwarder.json", payment_forwarder)
                 payment_forwarder_contract.functions.isTermsOfServiceEnabled().call()
+                terms_of_service_address = payment_forwarder_contract.functions.termsOfService().call()
+                terms_of_service_contract = get_deployed_contract(web3, "terms-of-service/TermsOfService.json", terms_of_service_address)
+
             except (ValueError, ContractLogicError):
                 # EVMTester will give ValueError if the function does not exist
                 # Legacy
@@ -411,6 +422,7 @@ def fetch(
             generic_adapter_contract,
             payment_forwarder_contract,
             guard_contract,
+            terms_of_service_contract,
             deployed_at_block=deployed_at_block,
             nominated_owner=nominated_owner,
             asset_manager=asset_manager,  # We cannot read asset manager back from the vault because it's just EVM hash map

tests/enzyme/test_guard_enzyme_uniswap_v2.py

@@ -295,6 +295,12 @@ def test_enzyme_usdc_payment_forwarder_transfer_with_authorization_and_terms(
     assert terms_of_service.functions.canAddressProceed(vault_investor.address).call()
 
 
+def test_fetch_terms_of_service(web3: Web3, vault: Vault):
+    """Resolve terms of service based on the vault."""
+    vault2 = Vault.fetch(web3, vault.address, payment_forwarder=vault.payment_forwarder.address)
+    assert vault2.terms_of_service_contract is not None
+
+
 def test_enzyme_guarded_trade_singlehop_uniswap_v2(
     web3: Web3,
     deployer: HexAddress,