Send a plaintext link to the mapreduce console in fluent style

The link was previously being sent using a JS redirect, which doesn't work
because the endpoints that trigger mapreduces can only be hit from the command
line (because they require auth). This commit switches the link to be in
plaintext and renders the full URL instead of just the path, so that clicking it
directly from the terminal works.

This also improves how these links are sent from callsites by using a fluent
style.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=228764606

java/google/registry/util/PipelineUtils.java

@@ -1,27 +0,0 @@
-// Copyright 2017 The Nomulus Authors. All Rights Reserved.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-package google.registry.util;
-
-/** Utilities for working with pipeline jobs. */
-public class PipelineUtils {
-
-  private static final String URL_PREFIX = "/_ah/pipeline/status.html?root=";
-
-  private PipelineUtils() {}
-
-  public static String createJobPath(String jobId) {
-    return URL_PREFIX + jobId;
-  }
-}