{auto} when wrapping a tagger around a channel that already has an error-callback installed, we should preserve the old callback

include/amqpcpp/channelimpl.h

@@ -207,6 +207,14 @@ public:
         // connection is gone
         _connection = nullptr;
     }
+    
+    /**
+     *  Expose the currently installed callbacks
+     *  @return ErrorCallback
+     */
+    const ErrorCallback &onError() const { return _errorCallback; }
+    const SuccessCallback &onReady() const { return _readyCallback; }
+    
 
     /**
      *  Callback that is called when the channel was succesfully created.

src/tagger.cpp

@@ -4,7 +4,7 @@
  *  Implementation for Tagger class.
  *  
  *  @author Michael van der Werve <michael.vanderwerve@mailerq.com>
- *  @copyright 2020 Copernica BV
+ *  @copyright 2020 - 2023 Copernica BV
  */
 
 /**
@@ -34,6 +34,9 @@ Tagger::Tagger(Channel &channel) : _implementation(channel._implementation)
     // we might have failed, in which case we throw
     if (!deferred) throw std::runtime_error("could not enable publisher confirms");
 
+    // remember the original callback
+    _errorCallback = _implementation->onError();
+
     // we wrap a handling error callback that calls our member function
     _implementation->onError([this](const char *message) { reportError(message); });  
 }