Add underlying token

Author: prevostc

schema.graphql

@@ -44,6 +44,9 @@ type BeefyVault @entity {
   "Moo token address"
   sharesToken: Token!
 
+  "Underlying token address"
+  underlyingToken: Token!
+
   "The vault's strategy"
   strategy: BeefyStrategy!
 

src/entity/vault.ts

@@ -24,6 +24,7 @@ export function getBeefyVault(vaultAddress: Bytes): BeefyVault {
   if (!vault) {
     vault = new BeefyVault(vaultAddress)
     vault.sharesToken = ADDRESS_ZERO
+    vault.underlyingToken = ADDRESS_ZERO
     vault.strategy = ADDRESS_ZERO
     vault.isInitialized = false
     vault.initializedAtBlockNumber = ZERO_BI

src/vault-lifecycle.ts

@@ -100,9 +100,15 @@ export function handleStrategyInitialized(event: ethereum.Event): void {
  */
 function fetchInitialVaultData(vault: BeefyVault): BeefyVault {
   const vaultAddress = Address.fromBytes(vault.id)
+  const vaultContract = BeefyVaultV7Contract.bind(vaultAddress)
+
+  const underlyingTokenAddress = vaultContract.want()
+
   const sharesToken = getTokenAndInitIfNeeded(vaultAddress)
+  const underlyingToken = getTokenAndInitIfNeeded(underlyingTokenAddress)
 
   vault.sharesToken = sharesToken.id
+  vault.underlyingToken = underlyingToken.id
   vault.lifecycle = BEEFY_VAULT_LIFECYCLE_RUNNING
 
   return vault