Merge bitcoin/bitcoin#36251: rest: add `generated` and `height` to spenttxouts JSON

### doc/REST-interface.md
@@ -97,6 +97,7 @@ Responds with 404 if block not found.
 Given a block hash: returns a collection of spent transaction output lists,
 one per transaction in the block.
 Responds with 404 if the block doesn't exist or its undo data is not available.
+The JSON format matches the prevout objects of the `getblock` RPC with verbosity 3.
 
 #### Chaininfos
 `GET /rest/chaininfo.json`

### doc/release-notes-36251.md
@@ -0,0 +1,7 @@
+Updated REST APIs
+-----------------
+
+- The `/rest/spenttxouts/BLOCKHASH.json` endpoint now includes the `generated`
+  (whether the previous output is a coinbase output) and `height` fields for
+  each previous output, matching the `prevout` objects of the `getblock` RPC
+  with verbosity 3. The binary and hex formats are unchanged.

### src/rest.cpp
@@ -325,6 +325,8 @@ static void BlockUndoToJSON(const CBlockUndo& block_undo, UniValue& result)
         UniValue tx_prevouts(UniValue::VARR);
         for (const Coin& coin : tx_undo.vprevout) {
             UniValue prevout(UniValue::VOBJ);
+            prevout.pushKV("generated", coin.IsCoinBase());
+            prevout.pushKV("height", coin.nHeight);
             prevout.pushKV("value", ValueFromAmount(coin.out.nValue));
 
             UniValue script_pub_key(UniValue::VOBJ);

### test/functional/interface_rest.py
@@ -451,14 +451,12 @@ def run_test(self):
 
             for i, tx in enumerate(block["tx"]):
                 prevouts = [txin["prevout"] for txin in tx["vin"] if "coinbase" not in txin]
-                # compare with `getblock` JSON output (coinbase tx has no prevouts)
+                # compare binary REST format with `getblock` JSON output (coinbase tx has no prevouts)
                 actual = [(txout.scriptPubKey.hex(), Decimal(txout.nValue) / COIN) for txout in spent[i]]
                 expected = [(p["scriptPubKey"]["hex"], p["value"]) for p in prevouts]
                 assert_equal(expected, actual)
-                # also compare JSON format
-                actual = [(prevout["scriptPubKey"], prevout["value"]) for prevout in spent_json[i]]
-                expected = [(p["scriptPubKey"], p["value"]) for p in prevouts]
-                assert_equal(expected, actual)
+                # also compare the JSON REST format to the getblock verbosity 3 RPC output
+                assert_equal(spent_json[i], prevouts)
 
         self.log.info("Test the /blockpart URI")