Implement config service cache on top of datastore

appengine/gaemiddleware/routes.go

 // Copyright 2015 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 gaemiddleware
 
 import (
         "github.com/luci/luci-go/server/router"
         "github.com/luci/luci-go/server/settings/admin"
 
         gaeauth "github.com/luci/luci-go/appengine/gaeauth/server"
         "github.com/luci/luci-go/appengine/tsmon"
+        "github.com/luci/luci-go/luci_config/appengine/gaeconfig"
 )
 
 // InstallHandlers installs HTTP handlers for various default routes.
 //
 // These routes are needed for various services provided in BaseProd context to
 // work (e.g. authentication related routes, time series monitoring, etc).
 //
 // 'base' is expected to be BaseProd() or its derivative. It must NOT do any
 // interception of requests (e.g. checking and rejecting unauthenticated
 // requests). It may inject additional state in the context though, if it is
 // needed by various tsmon callbacks or settings pages.
 //
 // In majority of cases 'base' should just be BaseProd(). If unsure what to use,
 // use BaseProd().
 func InstallHandlers(r *router.Router, base router.MiddlewareChain) {
         gaeauth.InstallHandlers(r, base)
         tsmon.InstallHandlers(r, base)
         admin.InstallHandlers(r, base, &gaeauth.UsersAPIAuthMethod{})
+        gaeconfig.InstallCacheCronHandler(r, base.Extend(RequireCron))
 }