stated a migration path from AASM version 3 to 4

HOWTO_MIGRATE_FROM_AASM_3_TO_4.md

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+# How to migrate from AASM version 3 to 4?
+
+## callback arguments
+
+On one hand, when using callbacks like this
+
+```ruby
+class MyClass
+  aasm do
+    ...
+    event :close, :before => :before do
+      transitions :to => :closed, :from => :open, :on_transition => :transition_proc
+    end
+  end
+  def transition_proc(arg1, arg2); end
+  def before(arg1, arg2); end
+  ...
+end
+```
+
+you don't have to provide the target state as first argument anymore. So, instead of
+
+```ruby
+my_class = MyClass.new
+my_class.close(:closed, arg1, arg2)
+```
+
+you can leave that away now
+
+```ruby
+my_class.close(arg1, args)
+```
+
+On the other hand, you have to accept the arguments for **all** callback methods (and procs)
+you provide and use. If you don't want to provide these, you can splat them
+
+```ruby
+def before(*args); end
+# or
+def before(*_); end # to indicate that you don't want to use the arguments
+```