Use cookies to store Discord auth code, validate all requests

[ngovil21]

Description

This updates the Discord Oauth to store the UserAuthCode using cookies and checks authorizations before the page loads

Motivation and Context

Fixes security issues with previous implementation.

How Has This Been Tested?

Limited testing on my production server. Would appreciate more reports.

Screenshots (if appropriate):

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)

Checklist:

• [x] My code follows the code style of this project.
• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.