Updating Guard contract to whitelist Gains/Ostium trading

[miohtama]

Update the GuardV0 smart contract to allow trading on Gains-compatible DEXes: Gains, Ostium.

1. Do a manual trading cycle of deposit/open/increse position/decrease position/close/redeem to find out what methods are called for trading
   • Alternatively check other Github repos that would have this information for Gains/Ostium like their unit test
   • Brainstorm and learn what could be potential security issues if the trading account private key is compromised: e.g. can we whitelist trading pairs, withdrawal addresses or such.
2. Add GuardV0 function "whitelistGainsTrading"
   • Whitelists all required smart contract call sites to be able to trade on Gains-compatible protocol
   • Create custom validators for Gains-smart contract calls that could be dangerous in the compromised asset manager private key situation
3. Create an end-to-end test case that whitelisting work
   • First figure out if we can do automated tests with mainnet fork or do we need to use testnet or even mainnet for testing this code
   • Tests deploy a new new guard smart contract "SimpleVault"
   • Tests must check the end-to-end path from 1) works and the vault can trade on Gains through all steps
   • Tests must check that for any custom validation paths we need do in Guard smart contract, we check for the negative results: for example if we can check for whitelisted trading pairs or tokens, there must be a test to check that non-whitelisted token gives a revert from the guard smart contract

[miohtama]

A related example test case:

https://github.com/tradingstrategy-ai/web3-ethereum-defi/blob/master/tests/orderly/test_orderly_guard_safe.py