Original commit: elastic/x-pack-elasticsearch@387d7cf939
* [DOCS] Clarify null behaviour in ML resources * [DOCS] Add category error information Original commit: elastic/x-pack-elasticsearch@21cdb4fb36
* [DOCS] Add ML categorization of messages * [DOCS] Describe ML categorization_examples_limit property * [DOCS] Updated ML categorization of messages * [DOCS] Add links to ML categorization Original commit: elastic/x-pack-elasticsearch@6403f6ce84