invoke smart wallet offer result without making a zoe offer

[dckc]

What is the Problem Being Solved?

pushPrice uses the continuing invitation pattern, which involves getting an invitation from the contract and making an offer via Zoe, when there is no exchange of assets.

Description of the Design

Add an invokeOfferResult(offerId, method, ...args) method to the smartWallet that would

1. look up the offer result corresponding to offerId
2. call E(offerResult).method(..args)

The smartWallet's method of choosing of which offerResults to retain might also need adjustment.

Security Considerations

when un-marshaling args, be sure not to create promises (cf. #5965)

Scaling Considerations

The offerId -> offerResult mapping grows without bound. Currently, we consider this manageable because it only occurs for continuing offers:

• for each vault created - and there's a charge for this
• for oracle operators
• for EC members

Test Plan

TBD

Upgrade Considerations

This would be an upgrade to the walletFactory.

[turadg]

Relevant discussion:

• mediate object methods in wallet (simple data-only args) #3901 (comment)
• continuing invitation pattern documentation#667

To put it simply: dapps have all of the domain specific knowledge, but none of the authority, and wallets have all of the authority and none of the domain specific knowledge.