Merge bitcoin/bitcoin#32517: rpc: add "ischange: true" to decoded tx outputs in wallet gettransaction response

060bb55508 rpc: add decoded tx details to gettransaction with extra wallet fields (Matthew Zipkin)
ad1c3bdba5 [move only] move DecodeTxDoc() to a common util file for sharing (Matthew Zipkin)
d633db5416 rpc: add "ischange: true" in wallet gettransaction decoded tx output (Matthew Zipkin)

Pull request description:

  This change is motivated by external RBF clients like https://github.com/CardCoins/additive-rbf-batcher/. It saves the user a redundant re-looping of tx outputs, calling `getaddressinfo` on each one, looking for the change output in order to adjust the fee.

  The field `"ischange"` only appears when `gettransaction` is called on a wallet, and is either `true` or not present at all. I chose not to include `ischange: false` because it is confusing to see that on *received* transactions.

  Example of the new field:

  ```
      "vout": [
        {
          "value": 1.00000000,
          "n": 0,
          "scriptPubKey": {
            "asm": "0 5483235e05c76273b3b50af62519738781aff021",
            "desc": "addr(bcrt1q2jpjxhs9ca388va4ptmz2xtns7q6lupppkw7wu)#d42g84j6",
            "hex": "00145483235e05c76273b3b50af62519738781aff021",
            "address": "bcrt1q2jpjxhs9ca388va4ptmz2xtns7q6lupppkw7wu",
            "type": "witness_v0_keyhash"
          }
        },
        {
          "value": 198.99859000,
          "n": 1,
          "scriptPubKey": {
            "asm": "0 870ab1ab58632b05a417d5295f4038500e407592",
            "desc": "addr(bcrt1qsu9tr26cvv4stfqh65547spc2q8yqavj7fnlju)#tgapemkv",
            "hex": "0014870ab1ab58632b05a417d5295f4038500e407592",
            "address": "bcrt1qsu9tr26cvv4stfqh65547spc2q8yqavj7fnlju",
            "type": "witness_v0_keyhash"
          },
          "ischange": true
        }
      ]

  ```

ACKs for top commit:
  furszy:
    ACK [060bb55](https://github.com/bitcoin/bitcoin/pull/32517/commits/060bb55508245776bb6a39c8b7849769ee588d69)
  maflcko:
    review ACK 060bb55508 🌛
  achow101:
    ACK 060bb55508
  rkrux:
    lgtm ACK 060bb55508

Tree-SHA512: aae4854d2bb4e9a7bc1152691ea90e594e8da8a63c9c7fda72a504fb6a7e54ae274ed5fa98d35d270e0829cc8f8d2fd35a5fc9735c252a10aa42cc22828930e7

src/wallet/rpc/transactions.cpp

@@ -7,6 +7,7 @@
 #include <policy/rbf.h>
 #include <primitives/transaction_identifier.h>
 #include <rpc/util.h>
+#include <rpc/rawtransaction_util.h>
 #include <rpc/blockchain.h>
 #include <util/vector.h>
 #include <wallet/receive.h>
@@ -700,7 +701,7 @@ RPCHelpMan gettransaction()
                         {RPCResult::Type::STR_HEX, "hex", "Raw data for transaction"},
                         {RPCResult::Type::OBJ, "decoded", /*optional=*/true, "The decoded transaction (only present when `verbose` is passed)",
                         {
-                            {RPCResult::Type::ELISION, "", "Equivalent to the RPC decoderawtransaction method, or the RPC getrawtransaction method when `verbose` is passed."},
+                            DecodeTxDoc(/*txid_field_doc=*/"The transaction id", /*wallet=*/true),
                         }},
                         RESULT_LAST_PROCESSED_BLOCK,
                     })
@@ -752,7 +753,16 @@ RPCHelpMan gettransaction()
 
     if (verbose) {
         UniValue decoded(UniValue::VOBJ);
-        TxToUniv(*wtx.tx, /*block_hash=*/uint256(), /*entry=*/decoded, /*include_hex=*/false);
+        TxToUniv(*wtx.tx,
+                /*block_hash=*/uint256(),
+                /*entry=*/decoded,
+                /*include_hex=*/false,
+                /*txundo=*/nullptr,
+                /*verbosity=*/TxVerbosity::SHOW_DETAILS,
+                /*is_change_func=*/[&pwallet](const CTxOut& txout) EXCLUSIVE_LOCKS_REQUIRED(pwallet->cs_wallet) {
+                                        AssertLockHeld(pwallet->cs_wallet);
+                                        return OutputIsChange(*pwallet, txout);
+                                    });
         entry.pushKV("decoded", std::move(decoded));
     }