feat: handle image variation filter + add extra iptc keyword filter using exiftool

BREAKING CHANGE: Refs:#1
4 jobs for feature/filtered_avatar_theme in 38 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Test
passed pytest_3.6 #1153149

00:00:38

passed pytest_3.7 #1153148

00:00:37

passed pytest_3.8 #1153147

00:00:36

passed pytest_latest #1153146

00:00:37