Allow fee granters

[fkneeland-figure]

Crate

Relayer

Summary

Currently there is no way to do a fee grant for IBC txs.

Problem Definition

It would be a better experience for orgs using the Hermes relayer to be able to do a fee grant to the address that is used for handling ibc txs. Otherwise orgs with a large amount of ibc traffic will need to maintain a large amount of coin on the account handling ibc txs to ensure that they go through.

Proposal

Currently the granter field on fees is set to the empty string. There are a couple ways that we could allow fee granters to be set. One would be to do a query before setting fees to see if there is a fee granter set. Another way which would be a bit simpler is to simply allow a user of the Hermes relayer to set a granter in the config file.

Acceptance Criteria

There should be a convenient non-breaking way of optionally adding a fee granter in the Hermes relayer.

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[dualsystems]

and fee grant nice work