Core: Add signalAboutToOpenTransaction (#24049)

* Core: Add signalAboutToOpenTransaction

* change name to squash

* Update AutoTransaction.cpp

* Update Application.h

* reorder

* Update AutoTransaction.cpp

* Update Application.h

src/App/Application.h

@@ -251,6 +251,8 @@ public:
     boost::signals2::signal<void (const Document&)> signalRedoDocument;
     /// signal on application wide redo
     boost::signals2::signal<void ()> signalRedo;
+    /// signal before open active transaction
+    boost::signals2::signal<void (const std::string&)> signalBeforeOpenTransaction;
     /// signal before close/abort active transaction
     boost::signals2::signal<void (bool)> signalBeforeCloseTransaction;
     /// signal after close/abort active transaction

src/App/AutoTransaction.cpp

@@ -134,6 +134,8 @@ int Application::setActiveTransaction(const char* name, bool persist)
     if (!name || !name[0]) {
         name = "Command";
     }
+    
+    this->signalBeforeOpenTransaction(name);
 
     if (_activeTransactionGuard > 0 && getActiveTransaction()) {
         if (_activeTransactionTmpName) {