In this commit, we fix an issue that was recently introduced as a result
of migration #10. The new TLV format ended up modifying the
serialization functions called in `serializePaymentAttemptInfo`.
Migration #9, also used this `serializePaymentAttemptInfo` method to
serialize the _new_ (pre TLV, but new payment attempt structure) routes
into the database during its migration. However, migration #10 failed to
copy over the existing unmodified `serializePaymentAttemptInfo` method
into the legacy serialization for migration #9. As a result, once
migration #9 was run, the routes/payments were serialized using the
_new_ format, rather than the format used for v0.7.1. This then lead to
de-serialization either failing, or causing partial payment corruption
as migration #10 was expecting the "legacy" format (no TLV info).
We fix this issue by adding a new fully enclosed
`serializePaymentAttemptInfoMigration9`method that will be used for
migration #9. Note that our tests didn't catch this, as they test the
migration in isolation, rather than in series which is how users will
encounter the migrations.
Fixes#3463.
This commit adds a set of htlcs to the Invoice struct and
serializes/deserializes this set to/from disk. It is a preparation for
accurate invoice accounting across restarts of lnd.
A migration is added for the invoice htlcs.
In addition to these changes, separate final cltv delta and expiry
invoice fields are created and populated. Previously it was required
to decode this from the stored payment request. The reason to create
a combined commit is to prevent multiple migrations.
