pdp API needs new endpoint: GET /pdp/proof-sets/{set-id}/roots/added/{txHash}

[rvagg]

Currently the transaction hash gets hidden internally. I propose that we make handleAddRootToProofSet similar to similar to handleCreateProofSet and have it return (approximately) this:

	w.Header().Set("Location", "/pdp/proof-sets/{set-id}/roots/added/{txHash}")

And then a new API, like /pdp/proof-sets/created, that can look up the status of the AddProofSet transaction and print out the status.

Then a client can know when, and whether, Curio has accepted the piece because it sees the chain has.

It would also be good to have handleGetProofSetRoot implemented so we can look up details once it's properly created.

[ZenGround0]

I'm fine with doing this and returning the Tx is clearly important, but why delegate the eth call stuff to curio? Why not just return the tx hash and then ask rpc api?

[rvagg]

@ZenGround0 similar (but not quite the same) to the create-proofset situation - Curio's timeline is different to the chain's. We get the tx from Curio for create-proofset, watch it land on chain, are happy with it from the client end, but it takes another 30-60s for Curio to report that it's happy with it. If we proceed after we see it land on chain then we get a failure.

That's handled here, but Curio is always well behind the chain when you watch it in action: https://github.com/FilOzone/synapse-sdk/blob/2482e2cdcbccb8941d3d1cc8365f2081ea6d3551/src/pandora/service.ts#L443-L459

It's not quite the same for add-roots because with create-proofsets we rely on Curio agreeing that it's created before we can add roots, but with add-roots it should be a stand-alone operation. However, it would be nice to know (a) that Curio agrees that it's added and it's going to start proving it, just for completeness and knowing that Curio didn't error or find disagreement somewhere, and (b) I'm a bit concerned about state management since we need to bake in nextRootId, how rapidly can we follow up with another addRoot, can we do it when we see the tx land but before Curio is happy that it's landed?

Mostly I want it so the client can be happy that it's both landed on chain and that Curio is actively proving it.