Update ERC-7786: Add `requestRelay`

[frangio]

Questions:

1. Should this functionality be in a contract separate from the gateway?
2. Should we define a quoting/estimation mechanism for gas price?
3. Should it be possible to pay with a different token?

[eip-review-bot]

✅ All reviewers have approved.

[cjcobb23]

3. Should it be possible to pay with a different token?

I don't think this should be part of the standard. I think gas services will implement this, but it shouldn't be required.

[cjcobb23]

2. Should we define a quoting/estimation mechanism for gas price?

I think so. I think more generally there should just be an estimate fee mechanism, that returns exactly what the user should pay to get the message delivered and executed. So it would also include any sort of fixed costs, in addition to the gas price.

[cjcobb23]

1. Should this functionality be in a contract separate from the gateway?

I think the gateway should include these functions, so that way everything a user needs to send a cross chain message is encapsulated in one contract. But it should be possible for a separate contract to implement just the gas service part of the interface, so that way users can use a different gas service than whatever is tied to the gateway.

[frangio]

This PR now builds on https://github.com/ethereum/ERCs/pull/1050 so until that PR is merged the diff in the Files tab is not helpful. I recommend looking at the diff here instead.

[github-actions[bot]]

The commit 86036fdfc646cfc19527ce2ba50c9c2ed17c16ef (as a parent of 74d561298fe87aa3f89b959275b284e9d4dcddad) contains errors. Please inspect the Run Summary for details.

[frangio]

Will propose as separate ERC in the future.