Add eslint to backend

[js0mmer]

Description

• Added eslint to the backend
• Fixed eslint errors
  • Refactored mongo helpers to fix eslint errors
    • could use some more work in the future. switch to mongoose?
  • Fixed types for some express routes/request objects
    • Could use more work. We are inconsistent with our typing and many routes do not have the request typed.
    • Response body isn't typed either.
    • This is something we can take care of when adding tRPC
• Updated packages
• Added a lint workflow

Steps to verify/test this change:

• Verify changes work as expected on staging instance
• Verify lint workflow works

Final Checks:

• Verify successful deployment

(optional)

• Write tests
• Write documentation

Issues

Closes #400

[github-actions]

Deployed staging instance to https://staging-404.peterportal.org