Ask translator class to read additional HDUs

This allows CFHT and DECam ingest to happen without a specialist
ingest task.

python/lsst/obs/base/ingest.py

@@ -29,7 +29,7 @@
 from collections import defaultdict
 from multiprocessing import Pool
 
-from astro_metadata_translator import ObservationInfo, merge_headers
+from astro_metadata_translator import ObservationInfo, merge_headers, MetadataTranslator
 from astro_metadata_translator.indexing import process_sidecar_data, process_index_data
 from lsst.afw.fits import readMetadata
 from lsst.daf.butler import (
@@ -367,7 +367,14 @@ def extractMetadata(self, filename: ButlerURI) -> RawFileData:
                 with filename.as_local() as local_file:
                     phdu = readMetadata(local_file.ospath, 0)
                     header = merge_headers([phdu, readMetadata(local_file.ospath)], mode="overwrite")
-            datasets = [self._calculate_dataset_info(header, filename)]
+
+                    # Try to work out a translator class.
+                    translator_class = MetadataTranslator.determine_translator(header, filename=filename)
+
+                    # Add each header to the dataset list
+                    datasets = [self._calculate_dataset_info(h, filename)
+                                for h in translator_class.read_all_headers(filename.ospath, header)]
+
         except Exception as e:
             self.log.debug("Problem extracting metadata from %s%s: %s", filename, sidecar_fail_msg, e)
             # Indicate to the caller that we failed to read.