feat(server/auth): HTTP_CONTROL_SERVER_AUTH_DEFAULT_ROLE option (JSON encoded)

- For example: `{"auth":"basic","username":"me","password":"pass"}`
- For example`{"auth":"apiKey","apikey":"xyz"}`
- For example`{"auth":"none"}` (I don't recommend)

Dockerfile

@@ -201,6 +201,7 @@ ENV VPN_SERVICE_PROVIDER=pia \
     HTTP_CONTROL_SERVER_LOG=on \
     HTTP_CONTROL_SERVER_ADDRESS=":8000" \
     HTTP_CONTROL_SERVER_AUTH_CONFIG_FILEPATH=/gluetun/auth/config.toml \
+    HTTP_CONTROL_SERVER_AUTH_DEFAULT_ROLE="{}" \
     # Server data updater
     UPDATER_PERIOD=0 \
     UPDATER_MIN_RATIO=0.8 \