chore: add shared sub-resource id path parameter

[wilsonianb]

We previously renamed sub-resource ids to incomingPaymentId, etc to disambiguate from the accompanying accountId path parameter.
accountId was removed in the switch to payment pointers, and sub-resource ids are now the lone path parameters.
This makes path parameters consistent with the auth server spec.

• inspired by addition of reusable parameter definitions in feat(OP-spec): add signature headers #187

[wilsonianb]

Yes or no on enforcing uuid?
interledger/rafiki#603 (comment)

[sabineschaller]

I vote no. That's a business decision.

[sabineschaller]

I like the change. I'm don't like that we need to change the implementation again. But I'm sure you'll do that @wilsonianb 😉

[wilsonianb]

I like the change. I'm don't like that we need to change the implementation again. But I'm sure you'll do that @wilsonianb wink

Yeah, I'll semi-revert this (as well as belatedly remove accountId):

• chore(backend): update route paths to match spec rafiki#373