Declare a system worker for generic dataset extraction

Closes #1894 (closed)

arkindex/process/models.py

@@ -723,6 +723,7 @@ class ArkindexFeature(Enum):
     InitElements = "init_elements"
     FileImport = "file_import"
     S3Ingest = "s3_ingest"
+    DatasetExtractor = "dataset_extractor"
     # When adding a new export worker, don't forget to also update the ExportFormat enum and the
     # FEATURE_FORMAT_MAP dictionary which maps export formats to arkindex features
     ExportPDF = "pdf_export"