fix latest CI breakages by forking code from grpc-go's interop/testing

Also moves testing package to internal/testing

internal/testing/cmd/bankdemo/auth.go

@@ -0,0 +1,49 @@
+package main
+
+import (
+	"strings"
+
+	"golang.org/x/net/context"
+	"google.golang.org/grpc/metadata"
+)
+
+func getCustomer(ctx context.Context) string {
+	// we'll just treat the "auth token" as if it is a
+	// customer ID, but reject tokens that begin with "agent"
+	// (those are auth tokens for support agents, not customers)
+	cust := getAuthCode(ctx)
+	if strings.HasPrefix(cust, "agent") {
+		return ""
+	}
+	return cust
+}
+
+func getAgent(ctx context.Context) string {
+	// we'll just treat the "auth token" as if it is an agent's
+	// user ID, but reject tokens that don't begin with "agent"
+	// (those are auth tokens for customers, not support agents)
+	agent := getAuthCode(ctx)
+	if !strings.HasPrefix(agent, "agent") {
+		return ""
+	}
+	return agent
+}
+
+func getAuthCode(ctx context.Context) string {
+	md, ok := metadata.FromIncomingContext(ctx)
+	if !ok {
+		return ""
+	}
+	vals := md.Get("authorization")
+	if len(vals) != 1 {
+		return ""
+	}
+	pieces := strings.SplitN(strings.ToLower(vals[0]), " ", 2)
+	if len(pieces) != 2 {
+		return ""
+	}
+	if pieces[0] != "token" {
+		return ""
+	}
+	return pieces[1]
+}