core: adding changes to auth.js and authcontext.js

[keanacobarde]

Description

• added baseline functionality to logging in and logging out for a user who already exists within the database.
• Still missing: register functionality. Another PR will be created for the register form component whenever it is implemented

Related Issue

3

Motivation and Context

• Required for the functionality of the frontend/backend.

How Can This Be Tested?

• Pull PR branch to local testing branch.
• Ensure that your user w/ a Firebase UID is added to the database
• Stand webserver and log in, you should be routed directly to the homepage

Screenshots (if appropriate):

N / A

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)