**Warning: This commit contains a database upgrade.**
In order to add future support for retiring xpub keys, the database is
upgraded such that the keys are now stored in a dedicated bucket which
can hold multiple values rather than storing a single key as individual
values in the root bucket.
A new ID field is added to distinguish between keys. This ID is added to
every ticket record in the database in order to track which pubkey was
used for each ticket.
A new field named "Retired" has also been added to pubkeys. It is a unix
timestamp representing the moment the key was retired, or zero for the
currently active key.
This removes all of the global loggers from the project and replaces them with loggers which are instantiated in vspd.go and passed down as params.
To support this, the background package was removed. It only contained one file so it was a bit pointless anyway. It only existed so background tasks could have their own named logger.
To allow signing with addresses other than the commitment address, add
an alternate signature address. In order to continue to prove that the
address was chosen by the user, add an alternate signature history. Only
allow one record per ticket to be saved to cap needed db space.
**NOTE: This contains a backwards incompatible database migration, so if you plan to test it, please make a copy of your database first.**
Moves tickets from a single database bucket containing JSON encoded strings, to a bucket for each ticket.
This change is to preemptively deal with scaling issues seen with databases containing tens of thousands of tickets.
