Update README.md

update passthru columns info

README.md

@@ -124,13 +124,16 @@ models:
       +schema: my_new_schema_name # leave blank for just the target_schema
 ```
 ### Adding Passthrough Columns
-This package allows users to add additional columns to the `salesforce__opportunity_enhanced`, `salesforce__opportunity_line_item_enhanced`, and `salesforce__contact_enhanced` model by using the below variables in your `dbt_project.yml` file.
+This package allows users to add additional columns to the `salesforce__opportunity_enhanced`, `salesforce__opportunity_line_item_enhanced`, and `salesforce__contact_enhanced` model by using the below variables in your `dbt_project.yml` file. These variables allow these additional columns to be aliased (`alias`) and casted (`transform_sql`) if desired, but not required. Datatype casting is configured via a sql snippet within the `transform_sql` key. You may add the desired sql while omitting the `as field_name` at the end and your custom pass-though fields will be casted accordingly. Use the below format for declaring the respective pass-through variables.
 
 For the `salesforce__opportunity_enhanced` model, it joins in the `user` model two times, since an opportunity has both an owner and manager. The first time the `user` model is joined is to add information about an opportunity owner. The second time is to add information about an opportunity manager. Therefore to avoid ambiguous columns from joining in the same model twice, custom fields passed through from the user table will be suffixed based on whether it belongs to a user who is an `_owner` or a `_manager`. 
 
 Additionally, you may add additional columns to the staging models. For example, for passing columns to `stg_salesforce__product_2` you would need to configure `salesforce__product_2_pass_through_columns`.
 
 ```yml
+# dbt_project.yml
+
+...
 vars:
   salesforce__account_pass_through_columns: 
     - name: "salesforce__account_field"