Creates or matches one account per array entry (by email) and writes the remaining keys as profile field values in a single pass. Company super-admin only.

Note the keys here are snake_case throughout — including first_name and last_name, which POST /users spells firstName/lastName. Unlike POST /users/{id}/data, empty values are ignored rather than clearing the field, and the response is only a count: it does not report skipped, pending-approval or unrecognised keys. Use POST /users/{id}/data when you need that feedback.