Create StudentsController.java, add GetById Endpoint for single record in students table

[smmzhu]

Overview

(Merge #28 before this one) Second ticket in a series tackling issue #26 — created StudentsController.java API endpoint controller, add GetById Endpoint for single record in students table + tests.

Testing Link: https://sampr2.dokku-11.cs.ucsb.edu/

Screenshots (Optional)

Validation (Optional)

1. Go into Swagger. Use the students Post request to create a student object in the table.
2. Validate this endpoint by using the GetById endpoint to get the student object back.
3. (for extra confirmation that admin perms are required) Try making a request on an account that does not have admin privileges. Make sure the request returns a 403.

Tests

• [x] Backend Unit tests (mvn test) pass
• [x] Backend Test coverage (mvn test jacoco:report) 100%
• [x] Backend Mutation tests (mvn test pitest:mutationCoverage) 100%
• [ ] Frontend Unit tests (npm test) pass
• [ ] Frontend Test coverage (npm run coverage) 100%
• [ ] Frontend Mutation tests (npx stryker run) 100%
• [ ] Frontend Linting (npx eslint --fix src)

Linked Issues

Closes #33

[Division7]

Heads up, if you're not ready to merge, you can mark the PR as a draft

[smmzhu]

*force-pushing at the end for cleaner viewing of files changed

(also i messed up resolving the merge conflicts on github.com directly so i just took my changes, rebased against updated main, and force pushed)

no code should be any different