Add full media fields to feed items query

[jhansche]

To remove the need for the local query override at https://github.com/PATROMO/bird-buddy-slack-bot/commit/744b9cd1017f4abc3bc5c0d71c68a951a7f59f32#diff-bcf8f09cccfbf0b38386a2482f92c843ee1d0acfd72ce8971eab11db8f08ad70