The types the trigger narrows to. Empty when one of definitions accepts
any document type, which leaves the trigger open to every document except
the engine's own.
The updates the trigger accepts: noUpdate for the watcher the
creates-only definitions share, otherwise its one definition's own.
One emitted start-watcher. A definition that watches updates has one to itself per watched dataset,
wf-<tag>-start-<dataset>-<definition>, so it never fires on a path only a sibling reads; the definitions that watch creates alone sharewf-<tag>-start-<dataset>-creates. Every'function'or'durableFunction'autonomous definition a document write can start gets one or the other. A'selfHosted'one gets neither, and appears in SelfHostedNeeds.startInstances instead.