format-dates: Error on date fields that do not exist

The user should be providing date fields that exist in the record.
Raise a loud error if a field does not exist!

augur/curate/format_dates.py

@@ -188,10 +188,8 @@ def run(args, records):
         for field in args.date_fields:
             date_string = record.get(field)
 
-            # TODO: This should raise an error if the expected date field does
-            # not exist in the the record
             if date_string is None:
-                continue
+                raise AugurError(f"Expected date field {field!r} not found in record {record_id!r}.")
 
             formatted_date_string = format_date(date_string, args.expected_date_formats)
             if formatted_date_string is None:

tests/functional/curate/cram/format-dates/date-field-not-found-error.t

@@ -0,0 +1,11 @@
+Setup
+
+  $ export AUGUR="${AUGUR:-$TESTDIR/../../../../../bin/augur}"
+
+Providing a date field that does not exist in the record should result in an error.
+
+  $ echo '{"record": 1, "date": "2024-01-01"}' \
+  >   | ${AUGUR} curate format-dates \
+  >     --date-fields "bad-date-field"
+  ERROR: Expected date field 'bad-date-field' not found in record 0.
+  [2]