In this commit, we extract the existing determineFeePerKw method on the
RPC server into a new file in the sweep package. Along the way, we
consolidate code by introducing a new FeePreference struct, which allows
the caller to express their fee preference either in blocks to
confirmation, or a direct fee rate. This move takes a small step to
father decoupling calls in the main RPC server.
In this commit, the sweep package is extended from just tx generation to
an active sweeper that collects sweep inputs and autonomously proceeds
to publish the sweep tx after the batch window time interval has passed
without new inputs being added.
In this commit, we modify the newly introduced UtxoSweeper.CreateSweepTx
to accept the confirmation target as a param of the method rather than a
struct level variable. We do this as this allows each caller to decide
at sweep time, what the fee rate should be, rather than using a global
value that is meant to work in all scenarios. For example, anytime
we're sweeping an output with a CLTV lock that's has a dependant
transaction we need to sweep/cancel, we may require a higher fee rate
than a regular force close with a CSV output.
This commit restores the sweep behavior of
filtering inputs with unknown witness types
from the final sweep transaction. Currently,
such inputs will be included without adding
anything to the weight estimate, possibly
creating a transaction with insufficient fees.
This commit introduces a common interface for sweep
inputs. It eliminates the type checking from UtxoSweeper.
Also the formerly present Amount() getter is removed. It was redundant
because this value is present in SignDesc().Output.Value as well.
