fix: build the course_id properly when MFE is deployed in a subdirectory

[jfavellar90]

This is a backport of https://github.com/edx/frontend-app-gradebook/pull/213

Developer Checklist

• [ ] Test suites passing
• [ ] Documentation and test plan updated, if applicable
• [ ] Received code-owner approving review
• [ ] Bumped version number package.json

Testing Instructions

[ How should a reviewer test this PR? ]

Reviewer Checklist

Collectively, these should be completed by reviewers of this PR:

• [ ] I've done a visual code review
• [ ] I've tested the new functionality

FYI: @edx/masters-devs-gta

[openedx-webhooks]

Thanks for the pull request, @jfavellar90! I've created OSPR-6326 to keep track of it in JIRA, where we prioritize reviews. Please note that it may take us up to several weeks or months to complete a review and merge your PR.

Feel free to add as much of the following information to the ticket as you can:

• supporting documentation
• Open edX discussion forum threads
• timeline information ("this must be merged by XX date", and why that is)
• partner information ("this is a course on edx.org")
• any other information that can help Product understand the context for the PR

All technical communication about the code itself will be done via the GitHub pull request interface. As a reminder, our process documentation is here.

Please let us know once your PR is ready for our review and all tests are green.

[openedx-webhooks]

@jfavellar90 🎉 Your pull request was merged! Please take a moment to answer a two question survey so we can improve your experience in the future.

[natabene]

@jfavellar90 @BbrSofiane Thank you!