Updated problem endpoint to return problem submissions.

* total_submissions and correct_submissions were returning problem part submissions

Incorporate no-id-professional mode into professional enrollments.

Doc: update course video data response values

Updated video endpoints to return users_at_start and users_at_end.

Video data API doc

Update fixture for answer_distribution. 

Make API compatible with old and new answer_dist schema.

Added video and video timeline endpoints.

Removed milliseconds from created date in problems endpoint.

Use docker for builds.

Updated Multiple Dependencies

Improved 404 Handling

The query to check if course data exists can be quite slow for some tables. Instead of running this query, we simply execute the actual query to retrieve data. If no data is returned, DRF will return a 404.

Do not build other branches unless they are part of a PR.

test-metrics git repo has moved.

Returning HTTP 503 if service is unhealthy

Fixing MySQL GROUP_CONCAT() Issues

Enable stats reporting to datadog.

Report coverage stats to datadog.

Updated Test Dependencies

The group_concat_max_len value needs to be increased for some courses. This value is specific to MySQL (as opposed to SQLite run locally), so the DB vendor must be compared to ensure the new code only runs for MySQL databases.

updating nr

Optimized Courses Problems Endpoint