preview_upload_mapping
STEP 1 of contact upload. Given the column headers from the user's spreadsheet/CSV, returns how each column maps to an Xmagnet field (standard fields + the tenant's saved custom fields). ALWAYS call this before upload_contacts and show the mapping to the user for confirmation. Unrecognized columns are auto-assigned to free custom_field slots.
Input Schema
| Name | Required | Description | Default |
|---|---|---|---|
| columns | Yes | Exact column header names from the user's file |