upgrade script

[ricomateo]

This PR introduces the following changes

• Adds a script that deploys a new stablecoin implementation for upgrades.
• Adds instructions for upgrading a stablecoin contract using a Safe multisig.
• Improves the stablecoin contract deployment script.

How to test

1. Start an anvil instance

2. Create a .env file with the following contents

   PRIVATE_KEY=0xac0974bec39a17e36ba4a6b4d238ff944bacb478cbed5efcae784d7bf4f2ff80
   STABLECOIN_NAME=Stablecoin
   STABLECOIN_SYMBOL=Stablecoin
   ADMIN_ADDRESS=0xf39Fd6e51aad88F6F4ce6aB8827279cffFb92266
   BURNER_ADDRESS=0xf39Fd6e51aad88F6F4ce6aB8827279cffFb92266
   PAUSER_ADDRESS=0xf39Fd6e51aad88F6F4ce6aB8827279cffFb92266
   FREEZER_ADDRESS=0xf39Fd6e51aad88F6F4ce6aB8827279cffFb92266

3. Create a src/StablecoinV2.sol file with the following contents

   // SPDX-License-Identifier: UNLICENSED
   pragma solidity ^0.8.13;
   import {Stablecoin} from "src/Stablecoin.sol";
   
   /// @custom:oz-upgrades-from Stablecoin
   contract StablecoinV2 is Stablecoin {
       function upgradeTest() public pure returns (uint8) {
           return 42;
       }
   }

   This contract will serve as the "new implementation"

4. Deploy the stablecoin with

   forge clean
   forge script script/DeployStablecoin.s.sol:DeployStablecoin  --broadcast --rpc-url http://localhost:8545

5. Deploy the new implementation with

   forge clean
   forge script script/DeployNewImplementation.s.sol --broadcast --rpc-url http://localhost:8545 \
   --sig 'run(string)' StablecoinV2.sol

6. Upgrade the contract to the new implementation with the following command (replacing STABLECOIN_ADDRESS and NEW_IMPLEMENTATION_ADDRESS with the addresses from steps 4 and 5, respectively)

   cast send --private-key 0xac0974bec39a17e36ba4a6b4d238ff944bacb478cbed5efcae784d7bf4f2ff80 --rpc-url http://localhost:8545 \
       STABLECOIN_ADDRESS 'upgradeToAndCall(address,bytes)()' NEW_IMPLEMENTATION_ADDRESS 0x 

7. Test the upgrade by calling the function upgradeTest, which is introduced in the StablecoinV2.sol contract

   cast call STABLECOIN_ADDRESS 'upgradeTest()(uint8)'

   If the contract was upgraded successfully, then the upgradeTest function will return 42.