Look up one field for each of up to 500 organizations in one call

The spreadsheet endpoint. Each row names an organization (an EIN, or a name to resolve) and ONE field from the published vocabulary (GET /api/v1/batch/fields); the values come back in the same order, each with a status that says whether it is an answer, an unresolved name, a field the key's plan does not reach, or an error. Costs one call per 50 rows rather than one per row, charged against the same allowance as every other endpoint. Rows the request cannot pay for are refused as a whole before any work is done, with the number of rows the balance does cover.