Extend LUCI_CONTEXT["local_auth"] protocol to understand accounts.

common/auth/localauth/ctx_test.go

 // Copyright 2017 The LUCI Authors. All rights reserved.
 // Use of this source code is governed under the Apache License, Version 2.0
 // that can be found in the LICENSE file.
 
 package localauth
 
 import (
         "testing"
         "time"
 
         "golang.org/x/net/context"
         "golang.org/x/oauth2"
 
         "github.com/luci/luci-go/common/clock"
         "github.com/luci/luci-go/common/clock/testclock"
         "github.com/luci/luci-go/lucictx"
 
         . "github.com/smartystreets/goconvey/convey"
 )
 
 func TestWithLocalAuth(t *testing.T) {
         t.Parallel()
 
         ctx := context.Background()
         ctx, _ = testclock.UseTime(ctx, testclock.TestRecentTimeLocal)
 
+        gen := func(ctx context.Context, scopes []string, lifetime time.Duration) (*oauth2.Token, error) {
+                return &oauth2.Token{
+                        AccessToken: "tok",
+                        Expiry:      clock.Now(ctx).Add(30 * time.Minute),
+                }, nil
+        }
+
         srv := Server{
-                TokenGenerator: func(ctx context.Context, scopes []string, lifetime time.Duration) (*oauth2.Token, error) {
-                        return &oauth2.Token{
-                                AccessToken: "tok",
-                                Expiry:      clock.Now(ctx).Add(30 * time.Minute),
-                        }, nil
-                },
+                TokenGenerators: map[string]TokenGenerator{"acc_id": gen},
         }
 
         Convey("Works", t, func() {
                 WithLocalAuth(ctx, &srv, func(ctx context.Context) error {
                         p := lucictx.GetLocalAuth(ctx)
                         So(p, ShouldNotBeNil)
                         req := prepReq(p, "/rpc/LuciLocalAuthService.GetOAuthToken", map[string]interface{}{
-                                "scopes": []string{"B", "A"},
-                                "secret": p.Secret,
+                                "scopes":     []string{"B", "A"},
+                                "secret":     p.Secret,
+                                "account_id": "acc_id",
                         })
                         So(call(req), ShouldEqual, `HTTP 200 (json): {"access_token":"tok","expiry":1454502906}`)
                         return nil
                 })
         })
 }