Added Mixin to disable rails Model callbacks via block for e.g. creating a User but not fetching the avatar.

lib/sequencer/unit/import/common/model/mixin/without_callback.rb

@@ -0,0 +1,55 @@
+class Sequencer
+  class Unit
+    module Import
+      module Common
+        module Model
+          module Mixin
+            module WithoutCallback
+              module ClassMethods
+
+                def without_callback(*callback)
+                  @callbacks ||= []
+                  @callbacks.push(callback)
+                end
+
+                def callbacks
+                  Array(@callbacks)
+                end
+              end
+
+              def self.prepended(base)
+                base.extend(ClassMethods)
+                base.uses :model_class
+              end
+
+              def process
+                # keep the super call as the last or only entry point
+                entry_point = proc do
+                  super
+                end
+
+                # loop over all registerd callbacks
+                self.class.callbacks.each do |callback|
+
+                  # create a duplicate of the previous entry point
+                  # to avoid an endless loop
+                  previous_entry_point = entry_point.dup
+
+                  # replace the previous entry point with a wrapped version
+                  # which skips the current callback
+                  entry_point = proc do
+                    model_class.without_callback(*callback, &previous_entry_point)
+                  end
+                end
+
+                # start at the last registerd entry point
+                # and go deep till we reach our super call
+                entry_point.call
+              end
+            end
+          end
+        end
+      end
+    end
+  end
+end