Custom save data containers are not possible

[gregorhcs]

We're using a save game framework where a single USaveGame is composed of "module" objects. We have one for each system, and would like to also add one for flow, which is not possible without hacks, since Flow requires UFlowSaveGame for save support.

In general it would be cool, if users weren't restricted to use UFlowSaveGame, but could also use their own USaveGame subclass.

My proposal is to introduce a IFlowSaveDataContainer interface, which provides methods to read and write flow save data, and refactor the save API of the UFlowSubsystem to work with that interface instead. UFlowSaveGame would then implement that interface and could still work as the default save solution for the plugin.

[gregorhcs]

I'm already working on an implemention for this: gregorhcs@6236194