Merge pull request #11277 from edx/PERF-251

cms/envs/common.py

common/djangoapps/clean_headers/__init__.py

common/djangoapps/clean_headers/decorators.py

common/djangoapps/clean_headers/middleware.py

common/djangoapps/clean_headers/tests/test_decorators.py

common/djangoapps/clean_headers/tests/test_middleware.py

common/djangoapps/contentserver/admin.py

common/djangoapps/contentserver/middleware.py

common/djangoapps/contentserver/migrations/0001_initial.py

common/djangoapps/contentserver/migrations/__init__.py

common/djangoapps/contentserver/models.py

common/djangoapps/contentserver/test/__init__.py

common/djangoapps/contentserver/test/test_contentserver.py

lms/envs/common.py