Switch from Guava Optionals to Java 8 Optionals

This was a surprisingly involved change. Some of the difficulties included
java.util.Optional purposely not being Serializable (so I had to move a
few Optionals in mapreduce classes to @Nullable) and having to add the Truth
Java8 extension library for assertion support.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=171863777

java/google/registry/tmch/LordnRequestInitializer.java

@@ -18,9 +18,9 @@ import static com.google.common.base.Verify.verifyNotNull;
 import static google.registry.util.UrlFetchUtils.setAuthorizationHeader;
 
 import com.google.appengine.api.urlfetch.HTTPRequest;
-import com.google.common.base.Optional;
 import google.registry.keyring.api.KeyModule.Key;
 import google.registry.model.registry.Registry;
+import java.util.Optional;
 import javax.inject.Inject;
 
 /** Helper class for setting the authorization header on a MarksDB LORDN request. */
@@ -41,7 +41,7 @@ final class LordnRequestInitializer {
           "lordnUsername is not set for %s.", Registry.get(tld).getTld());
       return Optional.of(String.format("%s:%s", lordnUsername, marksdbLordnPassword.get()));
     } else {
-      return Optional.absent();
+      return Optional.empty();
     }
   }
 }

java/google/registry/tmch/LordnTask.java

@@ -27,7 +27,6 @@ import com.google.appengine.api.taskqueue.TaskOptions.Method;
 import com.google.appengine.api.taskqueue.TransientFailureException;
 import com.google.apphosting.api.DeadlineExceededException;
 import com.google.common.base.Joiner;
-import com.google.common.base.Optional;
 import com.google.common.base.Strings;
 import com.google.common.collect.ImmutableList;
 import com.google.common.util.concurrent.Uninterruptibles;
@@ -35,6 +34,7 @@ import google.registry.model.domain.DomainResource;
 import google.registry.model.registrar.Registrar;
 import google.registry.util.NonFinalForTesting;
 import java.util.List;
+import java.util.Optional;
 import java.util.concurrent.TimeUnit;
 import org.joda.time.DateTime;
 import org.joda.time.Duration;

java/google/registry/tmch/Marksdb.java

@@ -24,7 +24,6 @@ import static javax.servlet.http.HttpServletResponse.SC_OK;
 import com.google.appengine.api.urlfetch.HTTPRequest;
 import com.google.appengine.api.urlfetch.HTTPResponse;
 import com.google.appengine.api.urlfetch.URLFetchService;
-import com.google.common.base.Optional;
 import com.google.common.io.ByteSource;
 import google.registry.config.RegistryConfig.Config;
 import google.registry.keyring.api.KeyModule.Key;
@@ -35,6 +34,7 @@ import java.net.URL;
 import java.security.Security;
 import java.security.SignatureException;
 import java.util.List;
+import java.util.Optional;
 import javax.annotation.Tainted;
 import javax.inject.Inject;
 import org.bouncycastle.jce.provider.BouncyCastleProvider;

java/google/registry/tmch/NordnUploadAction.java

@@ -34,7 +34,6 @@ import com.google.appengine.api.taskqueue.TaskOptions;
 import com.google.appengine.api.urlfetch.HTTPRequest;
 import com.google.appengine.api.urlfetch.HTTPResponse;
 import com.google.appengine.api.urlfetch.URLFetchService;
-import com.google.common.base.Optional;
 import google.registry.config.RegistryConfig.Config;
 import google.registry.request.Action;
 import google.registry.request.Parameter;
@@ -46,6 +45,7 @@ import google.registry.util.UrlFetchException;
 import java.io.IOException;
 import java.net.URL;
 import java.util.List;
+import java.util.Optional;
 import java.util.Random;
 import javax.inject.Inject;
 import org.joda.time.DateTime;

java/google/registry/tmch/TmchCrlAction.java

@@ -17,13 +17,13 @@ package google.registry.tmch;
 import static google.registry.request.Action.Method.POST;
 import static java.nio.charset.StandardCharsets.UTF_8;
 
-import com.google.common.base.Optional;
 import google.registry.config.RegistryConfig.Config;
 import google.registry.request.Action;
 import google.registry.request.auth.Auth;
 import java.io.IOException;
 import java.net.URL;
 import java.security.GeneralSecurityException;
+import java.util.Optional;
 import javax.inject.Inject;
 
 /** Action to download the latest ICANN TMCH CRL from MarksDB. */
@@ -45,7 +45,7 @@ public final class TmchCrlAction implements Runnable {
   public void run() {
     try {
       tmchCertificateAuthority.updateCrl(
-          new String(marksdb.fetch(tmchCrlUrl, Optional.<String>absent()), UTF_8),
+          new String(marksdb.fetch(tmchCrlUrl, Optional.<String>empty()), UTF_8),
           tmchCrlUrl.toString());
     } catch (IOException | GeneralSecurityException e) {
       throw new RuntimeException("Failed to update ICANN TMCH CRL.", e);

java/google/registry/tmch/TmchDnlAction.java

@@ -16,7 +16,6 @@ package google.registry.tmch;
 
 import static google.registry.request.Action.Method.POST;
 
-import com.google.common.base.Optional;
 import google.registry.keyring.api.KeyModule.Key;
 import google.registry.model.tmch.ClaimsListShard;
 import google.registry.request.Action;
@@ -25,6 +24,7 @@ import google.registry.util.FormattingLogger;
 import java.io.IOException;
 import java.security.SignatureException;
 import java.util.List;
+import java.util.Optional;
 import javax.inject.Inject;
 import org.bouncycastle.openpgp.PGPException;
 

java/google/registry/tmch/TmchSmdrlAction.java

@@ -16,7 +16,6 @@ package google.registry.tmch;
 
 import static google.registry.request.Action.Method.POST;
 
-import com.google.common.base.Optional;
 import google.registry.keyring.api.KeyModule.Key;
 import google.registry.model.smd.SignedMarkRevocationList;
 import google.registry.request.Action;
@@ -25,6 +24,7 @@ import google.registry.util.FormattingLogger;
 import java.io.IOException;
 import java.security.SignatureException;
 import java.util.List;
+import java.util.Optional;
 import javax.inject.Inject;
 import org.bouncycastle.openpgp.PGPException;