Exposing fees in ReverseSwapInfo

[danielgranhao]

Sending an onchain payment using a reverse swap results in a Payment that contains a ReverseSwapInfo. It would be useful if ReverseSwapInfo included the fees that were spent for the lockup and claim txs, as well as the swap provider fees. Right now we can only find out how much was spent on fees in total by comparing the sent LN funds and the resulting sent onchain funds.

[roeierez]

Thanks @danielgranhao.
If we are changing the ReveseSwapInfo then let's also add the payment_hash so users can use payment_by_hash method to retrieve the associated payment.

[JssDWt]

Working on exposing the reverse swap fees.
I can add the fees for any new reverse swap, but not existing ones, because we don't have the data.

I was thinking about backfilling the fees for the existing swaps by looking at onchain transaction fees. But the tx ids are only persisted in the local storage, not the sync storage. So this data is lost when you lose your local data.

So a 2-fold question to @danielgranhao and @roeierez:

• Is having the fees only for new swaps good enough?
• It seems to me like we should store the claim and lockup tx ids in the sync database, why are they in the local database only? (it was added in this PR Include ReverseSwapInfo in Payment #728)