OIDC: Set "no_body" option when authorizing against the 3scale backend

When using OIDC, the no_body option should be enabled when authorizing against the 3scale backend. This option helps reducing the workload in the 3scale backend, and also reduces network traffic.

Currently, the option is enabled always except when using OAuth. However, when using OIDC, the body returned by the 3scale backend is not parsed, so the no_body option should be enabled.