wallet: db, introduce 'RunWithinTxn()' helper function

'RunWithinTxn()' provides a way to execute db operations within a
transactional context. It avoids writing repetitive boilerplate code for
starting and committing the database transaction.

Author: furszy

src/wallet/wallet.cpp

@@ -2411,8 +2411,9 @@ bool CWallet::SetAddressBook(const CTxDestination& address, const std::string& s
 
 bool CWallet::DelAddressBook(const CTxDestination& address)
 {
-    WalletBatch batch(GetDatabase());
-    return DelAddressBookWithDB(batch, address);
+    return RunWithinTxn(GetDatabase(), /*process_desc=*/"address book entry removal", [&](WalletBatch& batch){
+        return DelAddressBookWithDB(batch, address);
+    });
 }
 
 bool CWallet::DelAddressBookWithDB(WalletBatch& batch, const CTxDestination& address)

src/wallet/walletdb.cpp

@@ -1230,6 +1230,30 @@ DBErrors WalletBatch::LoadWallet(CWallet* pwallet)
     return result;
 }
 
+bool RunWithinTxn(WalletDatabase& database, std::string_view process_desc, const std::function<bool(WalletBatch&)>& func)
+{
+    WalletBatch batch(database);
+    if (!batch.TxnBegin()) {
+        LogPrint(BCLog::WALLETDB, "Error: cannot create db txn for %s\n", process_desc);
+        return false;
+    }
+
+    // Run procedure
+    if (!func(batch)) {
+        LogPrint(BCLog::WALLETDB, "Error: %s failed\n", process_desc);
+        batch.TxnAbort();
+        return false;
+    }
+
+    if (!batch.TxnCommit()) {
+        LogPrint(BCLog::WALLETDB, "Error: cannot commit db txn for %s\n", process_desc);
+        return false;
+    }
+
+    // All good
+    return true;
+}
+
 void MaybeCompactWalletDB(WalletContext& context)
 {
     static std::atomic<bool> fOneThread(false);

src/wallet/walletdb.h

@@ -294,6 +294,20 @@ class WalletBatch
     WalletDatabase& m_database;
 };
 
+/**
+ * Executes the provided function 'func' within a database transaction context.
+ *
+ * This function ensures that all db modifications performed within 'func()' are
+ * atomically committed to the db at the end of the process. And, in case of a
+ * failure during execution, all performed changes are rolled back.
+ *
+ * @param database The db connection instance to perform the transaction on.
+ * @param process_desc A description of the process being executed, used for logging purposes in the event of a failure.
+ * @param func The function to be executed within the db txn context. It returns a boolean indicating whether to commit or roll back the txn.
+ * @return true if the db txn executed successfully, false otherwise.
+ */
+bool RunWithinTxn(WalletDatabase& database, std::string_view process_desc, const std::function<bool(WalletBatch&)>& func);
+
 //! Compacts BDB state so that wallet.dat is self-contained (if there are changes)
 void MaybeCompactWalletDB(WalletContext& context);