Importing data with Lookup fields using Azure Data Factory Common Data Service connector, when there is no ID field in source data

I have a customer who's migrating to a Common Data Service based application and needs a weekly data sync refresh. This data sync will upsert to a table from a CSV in Blob Storage to the Common Data Service for Apps connector.

The CSV data provides data for Lookup fields in CDS by their business key, and not the ID (GUID). Example: Instead of a Guid for an Account reference in the source file, the column will simply say "AT&T". It doesn't appear that Azure Data Factory's connector will resolve this Lookup value to an ID automatically even if there's an alternate key defined.

My question is what would be the best pattern for getting this data into CDS while having to resolve lookup IDs like this? Currently I'm copying Active Accounts into Azure Data Lake Gen 2 and performing a join using a mapping data flow in order to resolve the IDs. Is this the best option?