EDUCATOR-4638 | edx-bulk-grades==0.6.3 - make sure we pass a user_id attribute into GradeCSVProcessor.__init__()

Feanil/update for py3 fixes

This reverts commit a67b9f70a16a0f16a842aad84754b245a2480b5f,
reinstating commit cf78660ed35712f9bb7c112f70411179070d7382.
The original commit was reverted because I thought I found
bugs in it while verifying it on Stage, but it turns out that
it was simply misconfigured Stage data that causing errors.

The original commit's message has has been copied below:

This commit completes the program_enrollments LMS app
Python API for the time being. It does the following:
* Add bulk-lookup of users by external key in api/reading.py
* Add bulk-writing of program enrollments in api/writing.py
* Move grade-reading to api/grades.py
* Refactor api/linking.py to use api/writing.py
* Refactor signals.py to use api/linking.py
* Update rest_api/v1/views.py to utilize all these changes
* Update linking management command and support tool to use API
* Remove outdated tests from test_models.py
* Misc. cleanup

EDUCATOR-4321

* ENT-2294 | Moving utility functions in program enrollments to places related to the data they manipulate

* updating a mock path

* minor test fix

Awais786/bom 584

BOM-581

awais786/bom 594

PROD-687

BOM-457

test fixes

python 3 fixes

minor fixes

python 3 fixes

quality fixes

quality fixes

EDUCATOR-4670 - pr 1 - remove usage of persistsubsectionoride history

Merge pull request #21739 from edx/emma-green/REV-970/enterprise-users-should-not-get-first-purchase-discount

enterprise users should not get the first purchase discount

Making the regex that gets the index courses more secure

remove unused param

Rename cookie-policy-banner to frontend-component-cookie-policy-banner

BOM-736

This reverts commit af4e7a34.

After merging the above commit, I was seeing 'internal-error's
on Stage in responses to the Registrar API. I am temporarily
reverting it until I can figure out a fix.

quality fixes

python 3 fixes

quality fixes

BOM-724

Python3 fix.

Python3 fix.

BOM-637

Awais786/bom 482

Management command to add history to course_overviews_courseoverview.

Fixing python3

use the specified user from the parameter to determine if the flag is…

This commit completes the program_enrollments LMS app
Python API for the time being. It does the following:
* Add bulk-lookup of users by external key in api/reading.py
* Add bulk-writing of program enrollments in api/writing.py
* Move grade-reading to api/grades.py
* Refactor api/linking.py to use api/writing.py
* Refactor signals.py to use api/linking.py
* Update rest_api/v1/views.py to utilize all these changes
* Update linking management command and support tool to use API
* Remove outdated tests from test_models.py
* Misc. cleanup

EDUCATOR-4321