Make domain update flow handle null auth data (#2530)

It's valid for the auth data to be null (although it only happens 10 times
across our entire registry), so the domain update flow should not fail out with
a NullPointerException when the existing state of the data is null and the
update isn't adding that data either.

BUG=http://b/359264787

core/src/main/java/google/registry/flows/domain/DomainUpdateFlow.java

@@ -14,7 +14,6 @@
 
 package google.registry.flows.domain;
 
-import static com.google.common.base.MoreObjects.firstNonNull;
 import static com.google.common.collect.ImmutableSet.toImmutableSet;
 import static com.google.common.collect.ImmutableSortedSet.toImmutableSortedSet;
 import static com.google.common.collect.Sets.symmetricDifference;
@@ -282,7 +281,7 @@ public final class DomainUpdateFlow implements MutatingFlow {
             .removeContacts(remove.getContacts())
             .addContacts(add.getContacts())
             .setRegistrant(determineUpdatedRegistrant(change, domain))
-            .setAuthInfo(firstNonNull(change.getAuthInfo(), domain.getAuthInfo()));
+            .setAuthInfo(Optional.ofNullable(change.getAuthInfo()).orElse(domain.getAuthInfo()));
 
     if (!add.getNameservers().isEmpty()) {
       domainBuilder.addNameservers(add.getNameservers().stream().collect(toImmutableSet()));

core/src/main/java/google/registry/model/domain/DomainBase.java

@@ -144,6 +144,7 @@ public class DomainBase extends EppResource
     @AttributeOverride(name = "pw.value", column = @Column(name = "auth_info_value")),
     @AttributeOverride(name = "pw.repoId", column = @Column(name = "auth_info_repo_id")),
   })
+  @Nullable
   DomainAuthInfo authInfo;
 
   /** Data used to construct DS records for this domain. */
@@ -620,6 +621,7 @@ public class DomainBase extends EppResource
     return getAllContacts(true);
   }
 
+  @Nullable
   public DomainAuthInfo getAuthInfo() {
     return authInfo;
   }

core/src/main/java/google/registry/model/eppcommon/AuthInfo.java

@@ -16,6 +16,7 @@ package google.registry.model.eppcommon;
 
 import google.registry.model.ImmutableObject;
 import google.registry.model.UnsafeSerializable;
+import javax.annotation.Nullable;
 import javax.persistence.Embeddable;
 import javax.persistence.Embedded;
 import javax.persistence.MappedSuperclass;
@@ -49,10 +50,12 @@ public abstract class AuthInfo extends ImmutableObject implements UnsafeSerializ
   public static class PasswordAuth extends ImmutableObject implements UnsafeSerializable {
     @XmlValue
     @XmlJavaTypeAdapter(NormalizedStringAdapter.class)
+    @Nullable
     String value;
 
     @XmlAttribute(name = "roid")
     @XmlJavaTypeAdapter(CollapsedStringAdapter.class)
+    @Nullable
     String repoId;
 
     public String getValue() {
@@ -63,14 +66,14 @@ public abstract class AuthInfo extends ImmutableObject implements UnsafeSerializ
       return repoId;
     }
 
-    public static PasswordAuth create(String value, String repoId) {
+    public static PasswordAuth create(@Nullable String value, @Nullable String repoId) {
       PasswordAuth instance = new PasswordAuth();
       instance.value = value;
       instance.repoId = repoId;
       return instance;
     }
 
-    public static PasswordAuth create(String value) {
+    public static PasswordAuth create(@Nullable String value) {
       return create(value, null);
     }
   }