Rename PaymentFailed event

[TheBlueMatt]

We really need to rename the PaymentFailed event to indicate that sometimes its just a payment part or htlc that failed, not the full payment. see #1053 (comment)

[valentinewallace]

@jkczyz think we should rename to HTLCFailed? I'm not sure if that makes it weird to have an all_paths_failed field. I slightly prefer PaymentPathFailed for that reason.

[jkczyz]

If we go with the HTLC terminology, we could rename all_paths_failed to payment_failed perhaps. Note that for scoring we'll need an analogous event for success, possibly HTLCClaimed or PaymentPathSucceeded.

That said, HTLCs are an implementation detail that probably don't need to be exposed, especially given future payments may not use HTLCs. So perhaps the payment path terminology is more appropriate.

[valentinewallace]

HTLC does seem a little low-level for an event name, though other lightning impls have "htlc" in their public API, I'm not a huge fan but don't feel too strongly.

Happy to assign myself this issue if there's consensus on PaymentPathFailed or similar. I like PaymentPathSuccessfor the analogous success event

[jkczyz]

Sure, would you mind adding both events each including the path? Based on discussions in #1077, I'll keep the failing channel separate from the path.

[valentinewallace]

Oops

[valentinewallace]

@jkczyz For context, is scoring for successful paths going to be in V1? I thought we were starting with just avoiding previously failed routes

[jkczyz]

Yeah, I suppose it could wait until V2.