The following blog post in Planet doesn't show any images as they're using relative URLs which only work on the original domain:

https://planet.jboss.org/post/scheduling_voxxed_days_zurich_2018_with_optaplanner
https://www.optaplanner.org/blog/2018/02/19/SchedulingVoxxedDaysZurich2018.html

We should parse blog content as it's indexed to transform relative URLs to absolute URLs to pics this.