After upgrading a test cluster to 7.15.2 I see this warning when running Kibana queries in Discover constantly:
299 Elasticsearch-7.15.2-93d5a7f6192e8a1a12e154a2b81bf6fa7309da0c "Camel case format name dateOptionalTime is deprecated and will be removed in a future version. Use snake case name date_optional_time instead."
What is strange is that using the Kibana Inspect tab, I've tried running the query against ES directly and I don't get the warning back.