WIP #6: First working version after some cleanup

[renatomefi]

What has been done

• Some major cleanup in the events
• Added event type as enum and constants in event class

How to test

• Checkout the code and use the system normally

Todo

• Migrate the current events to the new one in order to keep production working
• Remove the Collections which are not used anymore
• Possibility to filter by event type
• What to do with the command handler? Keep it or not since this is a synchronous operation. (Talked to a friend and he usually has 2 queues, one is sync and the other isn't, this could be a solution in our case)

Notes

• This is a work in progress, please don't merge it!
• This is working but still with some issues
• Issue Improve Events mutations #6