mayagora/data exports should have to work as data imports.md

My [One Weird Hack](#one weird hack) idea for [adversarial interoperability](#adversarial interoperability) is that companies should be required to allow re-importing their exported data, with very limited security exceptions (honestly I haven't thought of any good ones, but let's say there are some). Along with existing hand wavey "you can't make the [format proprietary](#proprietary formats)" restrictions, this would mean that there would have to be some actual thought put into making the data usable and not capriciously changing the format. That would provide a more stable surface for other tools / companies to work against. 

You could argue this would "stifle innovation" but it seems like a company could always just trash anything [GDPR](#gdpr)-relevant that got in the way of a desired format change -- the laws are supposed to make it always easier to keep less data around, after all. 

I think you could make a case that this is necessary for meaningful consumer choice; I can't delete my data when I switch from photo-storage-provider X to photo-storage-provider Y without losing a bunch of [metadata](#metadata) I'd have to re-add if I wanted to switch back (and in the real case I'm thinking of, that'd be a pain in the ass).