* remove old_format reference in teams config

* validate uploaded character values for team csv upload

Co-authored-by: Ben Warzeski <benwarzeski@edX-C02CD0HCLVDM.cable.rcn.com>

AA-164: Performance fixes for course home

* remove old_format from team config tests

* remove old format from teams_config

Co-authored-by: Ben Warzeski <benwarzeski@edX-C02CD0HCLVDM.cable.rcn.com>

This reverts commit 1d7ff32a.

* Commits:
  Add is_staff check to masquerade POST
  Convert masquerade view to class-based

[CRI-174] [BB-2402] Fix LTI issues due to duplicated Content-Length header

AA-115: Adding external API for dates tab

This adds in the API for the Dates Tab for use by the
Course Home MFE.

Cleaned up a few more things about the testing configuration now that we've deployed Django 2.2 to production:

* Go back to a single version of django-oauth-toolkit, tox doesn't need to vary it anymore
* Go back to PyPI release of django-method-override
* Remove no longer needed dependency on python-oauth2 (we already removed the package it was used by)
* Update prepare_xdist_nodes.sh with new Django requirements file options

Remove code from the courseware index page that was only relevant if the shopping cart was enabled.

Restrict api to staff users

Optimization

** This removes some of the extra
   celery calls to credential service for
   updating grade when a certificate is updated.

** This removes extra db calls
   by reusing existing queryset values.

PROD-1363

Update swagger.yaml, fix some markup errors

* fix query to remove dulicates and incorrect teams

importing ENTERPRISE_CUSTOMERS_EXCLUDED_FROM_CATALOG list from settings following same pattern that is used for CORS_ORIGIN_WHITELIST

[AA-139] Record schedule updates to the history table when granting e…

Only the data download tab should appear for data researchers

TNL-7222

added reverse_sql method attribute to avoid sql operation error YONK-1588

* Commits:
  Check if user can upgrade prior to showing sock upgrade

AA-159: Improving performance of get_course_assignments