Add process_and_select_coins function

There were some common tasks identified in the construction of a coin
selection result that the different algorithms performed separately.
Those tasks were blended inside the algorithms or separated into
functions, but the underlying actions were the same:
- Do some preprocessing to the inputs.
- Select utxos based on the algorithm criterium.
- Decide change.
- Build the coin selection result.

This commit intends to create a single function that consumes different
algorithms and perform all the mentioned tasks as a pipeline taking
utxos as input and producing coin selection results at the end.

The new function reduces the work needed to implement other coin
selection algorithms, modularizes the code not related directly to the
selection process and reduces the number of lines to review and
understand its logic.

CHANGELOG.md

@@ -7,6 +7,18 @@ page. See [DEVELOPMENT_CYCLE.md](DEVELOPMENT_CYCLE.md) for more details.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [Unreleased]
+- Add capacity to create FeeRate from sats/kvbytes and sats/kwu.
+- Rename `as_sat_vb` to `as_sat_per_vb`. Move all `FeeRate` test to `types.rs`.
+- Add custom Harware Wallet Signer `HwiSigner` in `src/wallet/harwaresigner/` module.
+- Added `process_and_select_coins()` function.
+- Added `OutputGroup`s as a public structure that holds the `WeightedUtxo`, its
+  effective value, and its fees.
+- Changed `CoinSelectionAlgorithm::coin_select()` signature. The scope of the
+  selection was reduced to select utxos only from `optional_utxos`. It only
+  returns the selected `OutputGroups` from now on.
+- Added `WeightedScriptPubkey` struct.
+
 ## [v0.21.0] - [v0.20.0]
 
 - Add `descriptor::checksum::get_checksum_bytes` method.

src/types.rs

@@ -13,7 +13,7 @@ use std::convert::AsRef;
 use std::ops::Sub;
 
 use bitcoin::blockdata::transaction::{OutPoint, Transaction, TxOut};
-use bitcoin::{hash_types::Txid, util::psbt};
+use bitcoin::{hash_types::Txid, util::psbt, Script};
 
 use serde::{Deserialize, Serialize};
 
@@ -177,6 +177,18 @@ pub struct WeightedUtxo {
     pub utxo: Utxo,
 }
 
+/// A wallet owned script_pubkey with the weight of the `witness` + `scriptSig` in [weight units]
+/// to spend from it.
+/// Useful to optimize reducing the waste metric in coin selection algorithms.
+/// [weight units]: <https://en.bitcoin.it/wiki/Weight_units>
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct WeightedScriptPubkey {
+    /// The weight of the witness data and `scriptSig` expressed in [weight units].
+    pub satisfaction_weight: usize,
+    /// The script_pubkey
+    pub script_pubkey: Script,
+}
+
 #[derive(Debug, Clone, PartialEq)]
 /// An unspent transaction output (UTXO).
 pub enum Utxo {