用 ActiveModel::Callbacks 做 before, around, after callbacks

extend ActiveModel::Callbacks

```ruby

class Test

extend ActiveModel::Callbacks

define_model_callbacks :execute

before_execute :log_something

def index

run_callbacks :execute do

puts "Hi World!"

end

end

def log_something

puts "Log something..."

end

end

```

運行結果：
```
Development [1] rocket(main)> Test.new.index
Log something...
Hi World!
nil
```