feat: Implement keycloak protection for /admin endpoints

[raarielgrace]

Pull Request Standards

• The title of the PR is accurate
• The title includes the type of change [HOTFIX, FEATURE, etc]
• The PR title includes the ticket number in format of [NMP-###]
• Documentation is updated to reflect change

Description

This PR includes the following proposed change(s):

• Added dummy protected routes to API for the admin dashboard
• Redirect to /admin on login
• If user doesn't have admin role, redirect from /admin to landing page
• Added basic popup modal for error message (styling has some issues, but didn't bother altering in this PR)

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