The names of the fields to match within
The names of valid fields are available via PersonaStore.detail_key .
The ordering of the fields determines the order they are checked for matches, which can have performance implications (these should ideally be ordered from most- to least-likely to match).
Also note that more fields (particularly rarely-matched fields) will negatively impact performance, so only include important fields.
Default value is Query.MATCH_FIELDS_NAMES.