To be able to do MPP payment to multiple blinded routes we need
to add a constant dummy hop as a final hop to every blined path.
This is used when sending or querying a blinded path, to let the
pathfinder be able to send MPP payments over different blinded
routes. For this dummy final hop we use a NUMS key so that we
are sure no other node can use this blinded pubkey either in a
normal or blinded route.
Moreover this helps us handling the mission control data for
blinded paths correctly because we always consider the blinded
pubkey pairs which are registered with mission control when
a payment to a blinded path fails.
All the structs defined in the `channeldb/models` package are graph
related. So once we move all the graph CRUD code to the graph package,
it makes sense to have the schema structs there too. So this just moves
the `models` package over to `graph/db/models`.
If multiple blinded paths are provided, they will each have a different
pub key for the destination node. This makes using our existing
pathfinding logic tricky since it depends on having a single destination
node (characterised by a single pub key). We want to re-use this logic.
So what we do is swap out the pub keys of the destinaion hop with a
pseudo target pub key. This will then be used during pathfinding. Later
on once a path is found, we will swap the real destination keys back in
so that onion creation can be done.
This commit is purely a refactor. In it, we let the `BlindedEdge` struct
carry a pointer to the `BlindedPayment` that it was derived from. This
is done now because later on in the PR series, we will need more
information about the `BlindedPayment` that an edge was derived from.
Since we now pass in the whole BlindedPayment, we swap out the
`cipherText` member for a `hopIndex` member so that we dont carry around
two sources of truth in the same struct.
In the previous commit the AdditionalEdge interface was introduced
with both of its implementations `BlindedEdge` and `PrivateEdge`.
In both cases where we append a route either by a blinded route
section or private route hints we now use these new types. In
addition the `PayloadSizeFunc` type is introduced in the
`unifiedEdge` struct. This is necessary to have the payload size
function at hand when searching for a route hence not overshooting
the max sphinx package size of 1300 bytes.
Add the option to include a blinded route in a route request (exclusive
to including hop hints, because it's incongruous to include both), and
express the route as a chain of hop hints.
Using a chain of hints over a single hint to represent the whole path
allows us to re-use our route construction to fill in a lot of the
path on our behalf.
This commit adds a representation of blinded payments, which include a
blinded path and aggregate routing parameters to be used in payment to
the path.
