public interface PeerAuthenticatorPeer authenticators aim to verify the peer and run before
Authenticator. It returns false if authentication failed and stops handling the rest of the request; true if authentication succeeds and continue to execute rest of peer authenticators.
If no peer authenticator is set,
EndpointsPeerAuthenticatorwill be the default to verify the request is from Google. If you supply your own peer authenticator, make sure you also put
EndpointsPeerAuthenticatorto the head of peerAuthenticators list to verify the request is from Google.