Support LTI third-party-auth providers

common/djangoapps/student/helpers.py

common/djangoapps/student/views.py

common/djangoapps/third_party_auth/admin.py

common/djangoapps/third_party_auth/lti.py

...ps/third_party_auth/migrations/0004_lti_tool_consumers.py

common/djangoapps/third_party_auth/models.py

common/djangoapps/third_party_auth/pipeline.py

common/djangoapps/third_party_auth/provider.py

common/djangoapps/third_party_auth/strategy.py

...third_party_auth/tests/data/lti_cannot_add_get_params.txt

...on/djangoapps/third_party_auth/tests/data/lti_garbage.txt

...pps/third_party_auth/tests/data/lti_invalid_signature.txt

...ngoapps/third_party_auth/tests/data/lti_old_timestamp.txt

...ngoapps/third_party_auth/tests/data/lti_valid_request.txt

...rty_auth/tests/data/lti_valid_request_with_get_params.txt

common/djangoapps/third_party_auth/tests/specs/test_lti.py

.../djangoapps/third_party_auth/tests/specs/test_testshib.py

common/djangoapps/third_party_auth/tests/test_lti.py

common/djangoapps/third_party_auth/tests/testutil.py

common/djangoapps/third_party_auth/urls.py