Yes there are articles and the new Kibana Alerting is really nice. Here and most likely Here for your Use case the new DSL Query Alert.
However I think the hardest part no matter what you use will be the query / parsing that is why I asked for a few sample documents so perhaps we can help you with the query etc.
The Text analyzer will be breaking up that string into tokens which may or may or may not be easy to detect.
Example is it really
code [some message or code]
Please provide a couple sample documents and your mapping as well can you do that please.
Also please format your code / documents with the </> button above.
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