Add visited short URL info to every visit

[acelaya]

Part of #2180

In order to be able to relate every visit with the short URL that created it, this PR adds a new visitedShortUrl prop to every visit when serialized, which is an object with this type: array{shortCode: string, domain: string|null, shortUrl: string}

[acelaya]

There's a problem with this PR, because it adds N+1 queries, triggering a SELECT for the short URL and a SELECT for the domain, for every visit.

It could be that some have already been loaded, but I see it adds 10-20% overhead to the visits endpoint, which is already relatively slow.

It is probably better to build a more efficient query which loads visit, visit location, and potentially short URL and domain data beforehand, and check if that's more efficient.