Bumping k8s dependencies to 1.13

vendor/google.golang.org/grpc/Documentation/grpc-auth-support.md

@@ -21,6 +21,43 @@ server := grpc.NewServer(grpc.Creds(creds))
 server.Serve(lis)
 ```
 
+# OAuth2
+
+For an example of how to configure client and server to use OAuth2 tokens, see
+[here](https://github.com/grpc/grpc-go/blob/master/examples/oauth/).
+
+## Validating a token on the server
+
+Clients may use
+[metadata.MD](https://godoc.org/google.golang.org/grpc/metadata#MD)
+to store tokens and other authentication-related data. To gain access to the
+`metadata.MD` object, a server may use
+[metadata.FromIncomingContext](https://godoc.org/google.golang.org/grpc/metadata#FromIncomingContext).
+With a reference to `metadata.MD` on the server, one needs to simply lookup the
+`authorization` key. Note, all keys stored within `metadata.MD` are normalized
+to lowercase. See [here](https://godoc.org/google.golang.org/grpc/metadata#New).
+
+It is possible to configure token validation for all RPCs using an interceptor.
+A server may configure either a
+[grpc.UnaryInterceptor](https://godoc.org/google.golang.org/grpc#UnaryInterceptor)
+or a
+[grpc.StreamInterceptor](https://godoc.org/google.golang.org/grpc#StreamInterceptor).
+
+## Adding a token to all outgoing client RPCs
+
+To send an OAuth2 token with each RPC, a client may configure the
+`grpc.DialOption`
+[grpc.WithPerRPCCredentials](https://godoc.org/google.golang.org/grpc#WithPerRPCCredentials).
+Alternatively, a client may also use the `grpc.CallOption`
+[grpc.PerRPCCredentials](https://godoc.org/google.golang.org/grpc#PerRPCCredentials)
+on each invocation of an RPC.
+
+To create a `credentials.PerRPCCredentials`, use
+[oauth.NewOauthAccess](https://godoc.org/google.golang.org/grpc/credentials/oauth#NewOauthAccess).
+Note, the OAuth2 implementation of `grpc.PerRPCCredentials` requires a client to use
+[grpc.WithTransportCredentials](https://godoc.org/google.golang.org/grpc#WithTransportCredentials)
+to prevent any insecure transmission of tokens.
+
 # Authenticating with Google
 
 ## Google Compute Engine (GCE)