Only pay for used gas

[mdyring]

Users should only pay for gas consumed on a transaction, not the maximum allowance.

This is to prevent "fat finger" incidents (as seen on Cosmos Hub) and for fairness.

This seems in line with what IRISnet is doing: https://github.com/irisnet/irishub/blob/fdc78914a514ead0fc62d4773dcbae1a31b66fac/app/v1/auth/feeauth.go#L63

[blewater]

These SDK developments are relevant #51 (comment) and we need to consider that the transaction parameter GasWanted (--gas) is equivalent to GasLimit in Ethereum and functions correctly in the SDK.
Sure fees are taken in whole and that's a feature just like in Ethereum, BTC and even more relevant once the Cosmos SDK introduces prioritization cosmos/cosmos-sdk#9348
In any case, once the SDK introduces centralized fee management (per message ideally) cosmos/cosmos-sdk#9072 or we offer that along with the aforementioned Refund middleware we could address this issue.