When I send an alert through Kapacitor, either by defining one directly in TICKscript or by configuring one in Chronograf, I get to specify a Message using a template syntax. However, this syntax isn't documented in any great detail at https://docs.influxdata.com/kapacitor/v1.3/nodes/alert_node/#message; instead, the docs just provide a few examples.
What language are these templates even written in? Does the language have a name? Any documentation? How does its syntax work, and what can I do with it besides simply template in the variables listed in the docs?