Add nomulus count_domains command

This efficiently counts domains without having to load them (as opposed to the
existing list_domains command which does load then).

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=194559095

javatests/google/registry/tools/CountDomainsCommandTest.java

@@ -0,0 +1,70 @@
+// Copyright 2018 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.tools;
+
+import static google.registry.testing.DatastoreHelper.createTlds;
+import static google.registry.testing.DatastoreHelper.persistActiveDomain;
+import static google.registry.testing.DatastoreHelper.persistDeletedDomain;
+import static org.joda.time.DateTimeZone.UTC;
+
+import google.registry.model.ofy.Ofy;
+import google.registry.testing.FakeClock;
+import google.registry.testing.InjectRule;
+import org.joda.time.DateTime;
+import org.junit.Before;
+import org.junit.Rule;
+import org.junit.Test;
+
+/** Unit tests for {@link CountDomainsCommand}. */
+public class CountDomainsCommandTest extends CommandTestCase<CountDomainsCommand> {
+
+  protected FakeClock clock = new FakeClock(DateTime.now(UTC));
+
+  @Rule public final InjectRule inject = new InjectRule();
+
+  @Before
+  public final void before() {
+    inject.setStaticField(Ofy.class, "clock", clock);
+    command.clock = clock;
+    createTlds("foo", "bar", "baz", "qux");
+  }
+
+  @Test
+  public void testSuccess_singleTld() throws Exception {
+    for (int i = 0; i < 51; i++) {
+      persistActiveDomain(String.format("test-%d.foo", i));
+      if (i > 31) {
+        persistActiveDomain(String.format("test-%d.baz", i));
+      }
+    }
+    runCommand("foo");
+    assertStdoutIs("foo,51\n");
+  }
+
+  @Test
+  public void testSuccess_multipleTlds() throws Exception {
+    command.clock = clock;
+    for (int i = 0; i < 29; i++) {
+      persistActiveDomain(String.format("test-%d.foo", i));
+    }
+    for (int j = 0; j < 17; j++) {
+      persistActiveDomain(String.format("test-%d.baz", j));
+      persistDeletedDomain(String.format("del-%d.foo", j), clock.nowUtc().minusYears(1));
+    }
+    persistActiveDomain("not-counted.qux");
+    runCommand("foo", "bar", "baz");
+    assertStdoutIs("foo,29\nbar,0\nbaz,17\n");
+  }
+}