add calculateWithdrawableInterestAmountByPosition function for L1 and L2

Author: 0xkenta

lib/agent/lockup/calculateWithdrawableInterestAmountByPosition.ts

@@ -0,0 +1,18 @@
+import { getLockupContract } from './common'
+import { Provider } from '@ethersproject/abstract-provider'
+
+type Options = {
+	readonly provider: Provider
+	readonly positionTokenId: string
+}
+
+export const calculateWithdrawableInterestAmountByPosition = async (
+	options: Options
+): Promise<string | undefined> => {
+	const lockupContract = await getLockupContract(options.provider)
+	return lockupContract
+		? lockupContract.calculateWithdrawableInterestAmountByPosition(
+				options.positionTokenId
+		  )
+		: undefined
+}