Support outgoing payment withdrawal without event id

[wilsonianb]

Account provider may prefer to poll the state of a created and funded outgoing payment to check for completion/failure and withdraw remaining liquidity. Outgoing payment liquidity withdrawal is currently only possible with the outgoing_payment.completed/outgoing_payment.failed webhook event id: https://github.com/interledger/rafiki/blob/main/packages/backend/src/graphql/schema.graphql#L101

[wilsonianb]

This would require including the liquidity account balance in the query response. This could also be expanded to apply to incoming payments and payment pointers (SPSP)

[sabineschaller]

We need to re-evaluate whether we should decouple events from withdrawing liquidity.

[sabineschaller]

If we can query for events (by type), this should not be necessary anymore.

[wilsonianb]

I think @DonChangfoot inspired this issue from his initial Rafiki integration attempt. I'm not sure if it'd be preferable for an ASE to poll specific events vs a specific outgoing payment. I'm not not sure if we'd want or be able to support querying events by specific outgoing payment id.

[sabineschaller]

Thank you @wilsonianb. I'll check with @DonChangfoot.

[DonChangfoot]

Hey @sabineschaller @wilsonianb. Thanks for checking up on this

We prefer keeping track of just the id of the outgoing payment and mapping it 1-1 to our internal representation of it. We also prefer using the id of the payment to poll for its status, make a decision, and then make subsequent calls to drive it to the state we want.

Having a single id makes that a little easier. Hope that helps.