forums: fix assign_default_role to use the correct constant.
Fix the CoursePagesTest
trigger change event for file field while uploading pdf
STUD-1775
Add examples of html5 videos to docstrings.
Merge pull request #4104 from edx/alex/return_html5_video_sources_in_docstring_for_easy_testing

Add examples of html5 videos to docstrings.
implement forums endpoint for searching users
Merge pull request #4041 from edx/jsa/forums-search-users

implement forums endpoint for searching users.
Merge pull request #4089 from edx/zoldak/courses-test

Fix the CoursePagesTest
Merge pull request #4054 from edx/zub/bugfix/std1775-uploadpdfbutton

trigger change event for file field while uploading pdf
Revise course mode choose page.

LMS-2796