Removing duplicates from the /course/professors endpoint

[NathanP9000]

Grouping by the ids removes duplicate professors in the document

[mikehquan19]

@NathanP9000 , can you take a look at the conflicts?

[NathanP9000]

Sorry for the delay, before I finished fixing the conflicts I wanted to double check on the functionality of this endpoint and if my currently implemented fix would be acceptable.

The endpoint queries a specific course, joins its sections, and then joins the professors for each of those sections. However, one professor often teaches multiple sections, and this causes duplicate professor entries in the data stream.

When the $unwind and $replaceWith stages are executed, the professor data is fully extracted to the top level, but the original sections array from the course document is discarded. This results in a list of professors where the specific section context—which would explain the duplicates—is lost.

The Fix: My current implementation removes these duplicates to provide a clean list of unique professors. However, an alternative approach would be to refactor the pipeline to return unique combinations of professors and the specific sections they teach which would give more information than just returning the professors.