Add ORA2 dates to the dates page

ORA2 (openassessment) problems have multiple dates associated with are
not bound to the `due` date that is modified by Personalized Learner
Schedules. We expose the ORA2 dates separately in the dates page
so that learners aren't surprised by the differing deadlines.

[AA-223]

openedx/features/calendar_sync/tests/test_ics.py

@@ -41,10 +41,20 @@ class TestIcsGeneration(TestCase):
 
     def make_assigment(
         self, block_key=None, title=None, url=None, date=None, contains_gated_content=False, complete=False,
-        past_due=False, assignment_type=None
+        past_due=False, assignment_type=None, extra_info=None
     ):
         """ Bundles given info into a namedtupled like get_course_assignments returns """
-        return _Assignment(block_key, title, url, date, contains_gated_content, complete, past_due, assignment_type)
+        return _Assignment(
+            block_key,
+            title,
+            url,
+            date,
+            contains_gated_content,
+            complete,
+            past_due,
+            assignment_type,
+            extra_info
+        )
 
     def expected_ics(self, *assignments):
         """ Returns hardcoded expected ics strings for given assignments """