[Feature Request] Support syncing user data across a multi-server setup

[Sammster10]

Is your feature request related to a problem? Please describe.
When using in a multi-server setup, it can be annoying when the toggles get out of sync. It's nice to monitor MSPT in real time but I'd like to either have it on or off, across all servers. Using the boss bar toggle, for example.

Describe the solution you'd like
In modern versions supporting PersistentDataContainers (PDC) allow user data to be stored in the player PDC so plugins that sync data across multiple servers can be responsible for keeping this data in sync. There should be a config option for this, so both json files and the PDC are valid options.

Describe alternatives you've considered
I've considered a solution where data is stored in a remote database but this seems overkill for a couple toggles which don't need to be accessible offline. I can't justify the overhead that comes with a db in this case.

Additional context
The solution I described would work on spigot based servers, however after some quick research it seems that other supported servers (such as fabric) have a similar way to persist data on the player.