@Cacheable annotation is not clear

[tomaszmichalak]

I checked what factories are flagged with this annotation:

• Circuit Breaker Action
• HTTP Action
• Knot Action
• In-Memory Cache Action
• Inline Payload Action
• Inline Body Action

The stateful action is Circuit Breaker Action.

Other actions are stateless - it means that we would not break the logic by creating new instances each time. We added this annotation for better performance (I am guessing).

There are a few options what we can do:

• we remove this annotation and we care about instances in action factories - each factory decides if the new or existing instance is returned
  • we need to have a cache per action factory instance
  • custom action implementations are more complex
  • we duplicate the same code in many places
• move the annotation @Singleton to the io.knotx.fragments.action.api.ActionFactory#create method,
  • it is singleton per "action name", it means that we would get different instances for different action names
  • it is not easy to guess what is the reason for being singleton - stateful nature or some performance improvements
• introduce @Stateful and @Singleton annotations, they would have the same "behaviour" but they will be self-descriptive.

Originally posted by @tomaszmichalak in #154