Refactor the parsing logic to set up the reference between course and section using compound keys

[mikehquan19]

Refactor the parser in parser/courseParser.go and parser/sectionParser so that the course can reference the list of associated sections using their compound keys (combination of fields that uniquely identify the object) and vice versa.

For example, each course can be identified by:

{
   "subject_prefix": XX, 
   "course_number": YYYY, 
   "catalog_year": ZZ
}

instead of just mongo.Id (Same thing for section). How you want to set up this compound key is up to you as long as they are unique. You should only be concerned with the connection between course and section.

Refactoring the parser means that you will have to do the following things:

• Refactor the schema of course and section over the nebula-api repo
• Refactor the parsing logic between course and sections (main part)
• Refactor the course and section validating part in validator.go
• Refactor the test in courseParser_test.go, sectionParser_test.go, and validator_test.go.

While you work on this issue, make sure to pull or push to the compound-key branch that I created in both nebula-api & api-tools repo.

[mikehquan19]

@AtreyaG @SaKC124 @manjov123 Just pushed the POC to branch compound-key-approach, you can look at the code as reference. I removed all the tests in that branch as it's distracting, but you are supposed to modify the tests for the modified parsers.

[AtreyaG]

@mikehquan19 I pushed the refactored schemas to the compound-key branch in nebula-api. I should be good to push the refactored parsers in api-tools after the schemas are successfully merged.

[AtreyaG]

@mikehquan19 just pushed refactors parsers to compound-key in api-tools.