feat: add FeesDepositor spec

specs/protocol/jovian/fees-depositor.md

@@ -0,0 +1,117 @@
+# FeesDepositor
+
+<!-- START doctoc generated TOC please keep comment here to allow auto update -->
+<!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE -->
+
+- [Summary](#summary)
+- [Functions](#functions)
+  - [`receive`](#receive)
+  - [`setMinDepositAmount`](#setmindepositamount)
+  - [`setL2Recipient`](#setl2recipient)
+  - [`setGasLimit`](#setgaslimit)
+- [Events](#events)
+  - [`FeesDeposited`](#feesdeposited)
+  - [`MinDepositAmountUpdated`](#mindepositamountupdated)
+  - [`L2RecipientUpdated`](#l2recipientupdated)
+  - [`FundsReceived`](#fundsreceived)
+  - [`GasLimitUpdated`](#gaslimitupdated)
+
+<!-- END doctoc generated TOC please keep comment here to allow auto update -->
+
+## Summary
+
+A periphery contract on L1 that acts as a recipient of fees sent by the `L1Withdrawer` contract on L2. Its purpose is to perform a deposit transaction to OP Mainnet with those fees via the `OptimismPortal` once it has received sufficient funds.
+
+It's a proxied contract with the owner of the `ProxyAdmin` as the address allowed to call the setter functions.
+
+## Functions
+
+### `receive`
+
+Initiates the deposit transaction process to OP Mainnet if and only if the contract holds funds equal to or above the `minDepositAmount` threshold.
+
+```solidity
+receive() external payable
+```
+
+- MUST initiate a deposit transaction to the recipient on OP Mainnet if the `minDepositAmount` threshold is reached.
+- MUST emit the `FundsReceived` event with the sender, amount received, and the current balance of the contract.
+- MUST emit the `FeesDeposited` event only if the threshold is reached.
+
+### `setMinDepositAmount`
+
+Updates the minimum deposit amount the contract must hold before the deposit process can be initiated.
+
+```solidity
+function setMinDepositAmount(uint256 _newMinDepositAmount) external
+```
+
+- MUST only be callable by `ProxyAdmin.owner()`.
+- MUST emit the `MinDepositAmountUpdated` event.
+- MUST update the `minDepositAmount` storage variable.
+
+### `setL2Recipient`
+
+Updates the address that will receive the funds on OP Mainnet during the deposit process.
+
+```solidity
+function setL2Recipient(address _newRecipient) external
+```
+
+- MUST only be callable by `ProxyAdmin.owner()`.
+- MUST emit the `RecipientUpdated` event.
+- MUST update the `l2Recipient` storage variable.
+
+### `setGasLimit`
+
+Updates the gas limit used for the deposit transaction during the fees deposit process.
+
+```solidity
+function setGasLimit(uint64 _gasLimit) external
+```
+
+- MUST only be callable by `ProxyAdmin.owner()`.
+- MUST emit the `GasLimitUpdated` event.
+- MUST update the `gasLimit` storage variable.
+
+## Events
+
+### `FeesDeposited`
+
+Emitted when a deposit to OP Mainnet is initiated.
+
+```solidity
+event FeesDeposited(address indexed recipient, uint256 amount)
+```
+
+### `MinDepositAmountUpdated`
+
+Emitted when the minimum deposit amount before the deposit process can be initiated is updated.
+
+```solidity
+event MinDepositAmountUpdated(uint256 oldMinDepositAmount, uint256 newMinDepositAmount)
+```
+
+### `L2RecipientUpdated`
+
+Emitted when the recipient of the funds on OP Mainnet is updated.
+
+```solidity
+event L2RecipientUpdated(address oldL2Recipient, address newL2Recipient)
+```
+
+### `FundsReceived`
+
+Emitted whenever funds are received.
+
+```solidity
+event FundsReceived(address indexed sender, uint256 amount, uint256 newBalance)
+```
+
+### `GasLimitUpdated`
+
+Emitted when the gas limit for the deposit transaction is updated.
+
+```solidity
+event GasLimitUpdated(uint64 oldGasLimit, uint64 newGasLimit)
+```