Merge bitcoin/bitcoin#24118: Add 'sendall' RPC née sweep

bb84b7145b31dbfdcb4cf0b9b6e612a57e573993 add tests for no recipient and using send_max while inputs are specified (ishaanam)
49090ec4025152c847be8a5ab6aa6f379e345260 Add sendall RPC née sweep (Murch)
902793c7772e5bdd5aae5b0d20a32c02a1a6dc7c Extract FinishTransaction from send() (Murch)
6d2208a3f6849a3732af6ff010eeea629b9b10d0 Extract interpretation of fee estimation arguments (Murch)
a31d75e5fb5c1304445d698595079e29f3cd3a3a Elaborate error messages for outdated options (Murch)
35ed094e4b0e0554e609709f6ca1f7d17096882c Extract prevention of outdated option names (Murch)

Pull request description:

  Add sendall RPC née sweep

  _Motivation_
  Currently, the wallet uses a fSubtractFeeAmount (SFFO) flag on the
  recipients objects for all forms of sending calls. According to the
  commit discussion, this flag was chiefly introduced to permit sweeping
  without manually calculating the fees of transactions. However, the flag
  leads to unintuitive behavior and makes it more complicated to test
  many wallet RPCs exhaustively. We proposed to introduce a dedicated
  `sendall` RPC with the intention to cover this functionality.

  Since the proposal, it was discovered in further discussion that our
  proposed `sendall` rpc and SFFO have subtly different scopes of
  operation.
  • sendall:
    Use _given UTXOs_ to pay a destination the remainder after fees.
  • SFFO:
    Use a _given budget_ to pay an address the remainder after fees.

  While `sendall` will simplify cases of spending a given set of
  UTXOs such as paying the value from one or more specific UTXOs, emptying
  a wallet, or burning dust, we realized that there are some cases in
  which SFFO is used to pay other parties from a limited budget,
  which can often lead to the creation of change outputs. This cannot be
  easily replicated using `sendall` as it would require manual
  computation of the appropriate change amount.

  As such, sendall cannot replace all uses of SFFO, but it still has a
  different use case and will aid in simplifying some wallet calls and
  numerous wallet tests.

  _Sendall call details_
  The proposed sendall call builds a transaction from a specific
  subset of the wallet's UTXO pool (by default all of them) and assigns
  the funds to one or more receivers. Receivers can either be specified
  with a given amount or receive an equal share of the remaining
  unassigned funds. At least one recipient must be provided without
  assigned amount to collect the remainder. The `sendall` call will
  never create change. The call has a `send_max` option that changes the
  default behavior of spending all UTXOs ("no UTXO left behind"), to
  maximizing the output amount of the transaction by skipping uneconomic
  UTXOs. The `send_max` option is incompatible with providing a specific
  set of inputs.

  ---
  Edit: Replaced OP with latest commit message to reflect my updated motivation of the proposal.

ACKs for top commit:
  achow101:
    re-ACK bb84b7145b31dbfdcb4cf0b9b6e612a57e573993

Tree-SHA512: 20aaf75d268cb4b144f5d6437d33ec7b5f989256b3daeeb768ae1e7f39dc6b962af8223c5cb42ecc72dc38cecd921c53c077bc0ec300b994e902412213dd2cc3

1 files changed, 10 insertions, 0 deletions

diff --git a/doc/release-notes-24118.md b/doc/release-notes-24118.md
new file mode 100644
index 0000000000..16f23c7d00
--- /dev/null
+++ b/doc/release-notes-24118.md
@@ -0,0 +1,10 @@
+New RPCs
+--------
+
+- The `sendall` RPC spends specific UTXOs to one or more recipients
+  without creating change. By default, the `sendall` RPC will spend
+  every UTXO in the wallet. `sendall` is useful to empty wallets or to
+  create a changeless payment from select UTXOs. When creating a payment
+  from a specific amount for which the recipient incurs the transaction
+  fee, continue to use the `subtractfeefromamount` option via the
+  `send`, `sendtoaddress`, or `sendmany` RPCs. (#24118)