The Mixpanel property that this lookup table will be joined on. This defines
the "Join Key" — the Mixpanel event or user property whose values will be
matched against the property_key_column_name column in your warehouse table.
For example, if your events have a property called product_id and your warehouse
lookup table has a column product_id containing matching values along with
enrichment columns like product_name and category, you would set:
mixpanel_property.value = "product_id" (the Mixpanel property name)property_key_column_name = "product_id" (the warehouse column name)
