Remove incentive calculation from generalized methods. about aave-utilities

[sendra]

I would not put it in user, as the incentives are per reserve. I would create another separate method specific to calculate the incentives of a reserve.

The incentives part regarding the user. its only to calculate the reward that a user has, so its completely different than the reserve incentive api.

In my opinion, i think that doing a helper specific for this is the way to go. In fact it could also have methods for the user reward calculation, as i think this should also be extracted, as if the network does not have incentives, it doesnt make sense for the user to calculate its rewards

[joshstevens19]

@aschmidt20 once PR above is done you can use that in your user reserve one