Add boolean "image attached" property to news items

[georgelgeback]

Currently, the only way (?) for the frontend to know if a news item has an image attached is to send a request to the backend to try and fetch it. If we add a boolean property, we can avoid spamming the backend with a bunch of requests which will end up 404:ing anyway.

[omorros]

Hi, I'd like to take this issue. I'm thinking the solution would be adding a boolean property "has_image" to the news item model/response. Let me know if this approach is fine or you would prefer something else ;)