feat: added reporting audience check & audience token exchange

Added audience check based on auth provider identity. This is a temporary fix required by SLB because We want a non-fail check that reports only the missing audience. It is an SLB requirement specific to support clients' migration in September 2021. This fix will be temporarily used instead of the more generic JWKS PROXY. This fix will be removed and replaced in October 2021 with the generic JWKS PROXY.