Refactor serializers

[nickpfeiffer05]

Purpose

Lodash is unnecessary and can be replaced by native features. Serializer methods are better suited as static methods.

Tickets

https://github.com/orgs/sandboxnu/projects/20?pane=issue&itemId=80651976

Contributors

@Anzhuo-W , @nickpfeiffer05

Feature List

1. Removed reliance on Lodash in all serializer files
   • The previous serializers used many Lodash functions (.pick, .groupBy, etc.), that can now be replaced easily by modern JS features
   • PR has replaced all old Lodash functions with native JS
2. Conversion to static methods
   • Converted all serializer methods to static
   • Adjusted the use of serializers from instanced-calling to static-calling in searcher.ts

Reviewers

Primary:

@ananyaspatil

Secondary:

@mehallhm , @cherman23

[mehallhm]

Updating line 82 in the serializers/courseSerializer.ts breaks references in graphql/resolvers/class.ts. Updating the later to use the new static implementation of the method should clear the CI

[coveralls]

coverage: 80.613% (+0.1%) from 80.481%
when pulling a68d2b5 on refactor-serializers
into 33e48e4 on master.

[elvincheng3]

Are there any existing tests for the serializers? If so, we should update/add to them for new code changes; if not, we should write tests.

[elvincheng3]

Are there any existing tests for the serializers? If so, we should update/add to them for new code changes; if not, we should write tests.