Builds the field-values lookup for one entity: each field's value list, found by field name
(case-insensitive). Returns undefined when the entity or its fields are unknown, so a caller never
falls back to a same-named field on another entity.
Pure and browser-safe.
Builds the field-values lookup for one entity: each field's value list, found by field name (case-insensitive). Returns undefined when the entity or its fields are unknown, so a caller never falls back to a same-named field on another entity. Pure and browser-safe.