Slight rant: versioning a (REST) API inflicts upon you a confluence of factors that will lead to pain no matter what you do.
You’re going to need to version things, which opens you to bikeshedding which True Scotsman approach to REST versioning you’ll use. Once you’ve expended tons of effort on how clients should specify which version they want (i.e. once you’ve just barely started), now you need to figure out how to make that work in your code. Which, after you’re done parsing the HTTP request (the easy part!), is almost certainly going to lead to some unruly layer(s) of indirection. At which point you’re going to hate life and never want to introduce another version ever again. And you won’t even be close to finished.
I hope that, between JSON API and GraphQL, letting the client specify what they want ends up proving way better than relying on the server to carefully (or possibly carelessly) hand craft just the right data for the client.