Add authentication to `/query` route

[alyssadai]

• [x] add dependency of /query route on OAuth2 scheme
• [x] verify ID token from header using google-auth
• [x] read in client ID from env var, and error if unset
• [x] have option to turn off authentication

[neurobagel-bot[bot]]

:rocket: Issue was released in v0.3.0 :rocket: