ProctoredExamSoftwareSecureReview.video_url is nullable now

Set the video_url field on ProctoredExamSoftwareSecureReview table to be nullable.
This is the first step of removing the field.

Upgrade Django from 2.2 to 3.2

Upgraded the Django library used by this repo from 2.2 to 3.2.
Made adjustments on the CI process to reflect we no longer cares about django 2.2
Made library version upgrades to the latest.

4.2.0: Allow timed exams to be visible after course end date

Merge pull request #984 from edx/alangsto/timed_exams_should_be_visible

fix: timed exams should still be visible after course end date

4.1.3: Always allow practice exams to trigger grade and credit updates

Merge pull request #978 from edx/alangsto/allow_practice_exams_to_tri…

4.1.2: Use video url for PSI instructor dashboard url

Merge pull request #974 from edx/alangsto/use_video_url_in_redirect

feat: use video review url provided by PSI in redirect

4.1.1: Fix video url bug

Merge pull request #973 from edx/alangsto/redact_video_url

fix: redact video url from raw data

4.1.0: Capture video link from PSI and encrypt before storing

Merge pull request #969 from edx/alangsto/capture_video_review_link

feat: store encrypted video url from PSI

4.0.4: Replace jsonfield2 with jsonfield

• Switched from jsonfield2 to jsonfield as the earlier one has archived and merged back in the latter one.

4.0.3

chore: python package upgrades (incl. pylint) and style changes

JIRA:MST-1061

4.0.2

chore: fix pylint errors in some prod files for string formatting

JIRA:MST-1061