* add session type based on ecash ticket collection
* avoid setting session type if already set
* change duration type to duration
* add a cap for finished sessions
* add stats model
* add stats collection
* add stats route
* propagate stuff and run stuff
* cargo stuff
* sqlx unused what?
* add sessions started stat
* session durations in miliseconds
* apply Jon's comments
* [Product Data] Second step in gateway usage data collection (#4964)
* turn stats collection into event based
* move events into a common crate for future use elsewhere
* apply Jon's comments
Simon Wicky