Add suggested flag to instances-metadata

[dessalines]

No description provided.

[Nutomic]

Im currently making some changes in #586. Seems to me that having the suggested instances for each country in a single place is better.

https://github.com/LemmyNet/joinlemmy-site/pull/586/changes#diff-f78556500c68f47e12256acdcb2e85d0aa6847ba207adfd7344e2be7cce56af1R9

[dessalines]

This could work with that, you would just serialize the instances.filter(i => i.suggested) for the suggested endpoint.

[Nutomic]

Yes it would work, but then it becomes very difficult to see which instances are actually suggested. With changes in the other PR the logic is much more complex, and so its good to have it all in one place.

[dessalines]

I'm thinking now that the endpoint should probably just serialize the entire instances_metadata list. That'd be much more useful for apps to build their own in-app pickers. Or just use a simple dropdown.