For module engagement, parse the course ID from the URL

[doctoryes]

... when not present in the context.

https://openedx.atlassian.net/browse/DENG-606

Analytics Pipeline Pull Request

Make sure that the following steps are done before merging:

• [ ] If you have a migration please contact data engineering team before merging.
• [ ] Before merging run full acceptance tests suite and provide URL for the acceptance tests run.
• [ ] A member of data engineering team has approved the pull request.

[codecov[bot]]

Codecov Report

Merging #849 (95a22f3) into master (6f10185) will not change coverage. The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #849   +/-   ##
=======================================
  Coverage   74.02%   74.02%           
=======================================
  Files         208      208           
  Lines       23887    23887           
=======================================
  Hits        17683    17683           
  Misses       6204     6204           

Impacted Files	Coverage Δ
edx/analytics/tasks/insights/module_engagement.py	79.13% <100.00%> (ø)

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