modify volunteer/auth/donation route names to follow naming conventions

[ryanhu021]

Change volunteer, auth, and donation route names to follow route naming conventions. In volunteer.js, we have routes that should be grouped together, rather than having separate names. For example, all volunteer related routes should begin with /api/volunteer, followed by its specific sub-collection. Any requests in the frontend should also be updated to reflect this new convention.

• Auth routes are all routes containing /auth or using passport.<...>

Make sure you test these routes!