Returns the acceptable values for enumerable Opportunity
fields, plus reference lists for country, language, and
currency codes. Use this endpoint to populate picklist UI
controls so that the values an integrator surfaces stay in
step with the values the API accepts (which can be a subset
of the corresponding schema enum — see the PicklistOptions
schema for details).

The response is an object keyed by field path
(for example .customerInfo.customerDetails.address.regionCode);
each value is the array of acceptable
{ display, value } options for that field.

The response also contains a .dataMapper.stage key. This key
is a curated subset of the Stage enum used by Tackle's Data
Mapper feature when importing opportunity data from external
systems. It does not correspond to any field on the
Opportunity payload, and most integrators using this API
directly can ignore it.

Requires the cosell:GetPicklistOptions permission.