In this commit, we create a new chainfee package, that houses all fee
related functionality used within the codebase. The creation of this new
package furthers our long-term goal of extracting functionality from the
bloated `lnwallet` package into new distinct packages. Additionally,
this new packages resolves a class of import cycle that could arise if a
new package that was imported by something in `lnwallet` wanted to use
the existing fee related functions in the prior `lnwallet` package.
This commit is a step to split the lnwallet package. It puts the Input
interface and implementations in a separate package along with all their
dependencies from lnwallet.
In this commit, we add a new function, CraftSweepAllTx. This function
allows callers to craft a transaction which sweeps ALL outputs from the
wallet to a single target address. It can either be used for UTXO
consolidation (at the cost of privacy by co-mingling inputs), or simply
to sweep all funds out of a wallet for various reasons.
In an attempt to ensure this method is loosely coupled and testable, for
all behavior structs, we create brand new interface to accept. This
ensures that we only rely on the minimal number of methods needed to
perform our duty.
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.
