Merge branch 'implement_auth' into 'main'

backend/.env.template

backend/db/crud.py

backend/db/models.py

backend/db/schemas.py

backend/docker-compose.yml

backend/main.py

backend/routers/__init__.py

backend/routers/authentication.py

backend/routers/comments.py

frontend/.env.template

frontend/src/components/Comments.js

frontend/src/components/Header.js

frontend/src/global.css

frontend/src/index.js

frontend/src/styles/Comments.css

frontend/src/styles/Header.css