Trades for account endpoint: pagination doesn't work

[morleyzhi]

Here's a sample call to get trades on an account:

https://horizon.stellar.org/accounts/GAH3MQ6IJZ7QA4LT657AGUTVR7H3B3QQKBZ4Y4FKIASU7USAO5QTMH2X/trades?limit=2&order=desc

The links look like this:

  "_links": {
    "self": {
      "href": "https://horizon.stellar.org/accounts/GAH3MQ6IJZ7QA4LT657AGUTVR7H3B3QQKBZ4Y4FKIASU7USAO5QTMH2X/trades?cursor=\u0026limit=2\u0026order=desc"
    },
    "next": {
      "href": "https://horizon.stellar.org/accounts/GAH3MQ6IJZ7QA4LT657AGUTVR7H3B3QQKBZ4Y4FKIASU7USAO5QTMH2X/trades?cursor=78015765944496129-0\u0026limit=2\u0026order=desc"
    },
    "prev": {
      "href": "https://horizon.stellar.org/accounts/GAH3MQ6IJZ7QA4LT657AGUTVR7H3B3QQKBZ4Y4FKIASU7USAO5QTMH2X/trades?cursor=78081642152878081-0\u0026limit=2\u0026order=asc"
    }
  }

One thing looks wrong on its face: The "next" link is the same as the "prev" link with a different ordering mechanism, whereas you'd expect the difference to be different cursors.

Visiting the next link loads the same records as the initial call.