Unlimited Allowance

[rashtrakoff]

For upgrading ERC20 tokens to supertokens, we require providing allowance to the supertoken contract. This is done in individual strategy contracts. However, there is a chance that we might hit uint256 max amount (very unlikely but possible).

Suggest to check for allowance and also check if the top up is possible with the current allowance to the supertoken contract. If not, approve the contract once again.

The code for the same should ideally be in StrollManager.sol. However, to not break existing deployments, it's recommended to not change it from strategy contracts. However for the next version, see to it that it's moved. This will also help us with gas savings.