in client/src/main/scala/com.gu.contentapi.client/utils/CapiModelEnrichment.scala [171:175]
def isPillar(pillar: String): ContentFilter = content => content.pillarName.contains(pillar)
def hashedTagIds(content: Content) = content.tags.map { tag =>
DigestUtils.md5Hex(salt + tag.id)
}