Implement event for forum thread views

common/djangoapps/track/views/segmentio.py

common/djangoapps/track/views/tests/base.py

common/djangoapps/track/views/tests/test_segmentio.py

common/djangoapps/util/testing.py

lms/djangoapps/discussion/tests/test_views.py

lms/djangoapps/discussion/views.py

lms/djangoapps/django_comment_client/base/__init__.py

...angoapps/django_comment_client/base/event_transformers.py

lms/djangoapps/django_comment_client/base/tests.py

lms/djangoapps/django_comment_client/base/views.py

lms/djangoapps/django_comment_client/utils.py

lms/envs/common.py

lms/lib/comment_client/thread.py

lms/lib/comment_client/user.py