Change SendEmailService to an instance field.

This allows us to inject it with Dagger and avoid using InjectRule to set it
in unit tests.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=217571475

java/google/registry/reporting/icann/IcannReportingModule.java

@@ -25,7 +25,6 @@ import dagger.Provides;
 import google.registry.bigquery.BigqueryConnection;
 import google.registry.request.HttpException.BadRequestException;
 import google.registry.request.Parameter;
-import google.registry.util.SendEmailService;
 import java.lang.annotation.Documented;
 import java.lang.annotation.Retention;
 import java.util.Optional;
@@ -115,11 +114,6 @@ public final class IcannReportingModule {
     }
   }
 
-  @Provides
-  static SendEmailService provideSendEmailService() {
-    return new SendEmailService();
-  }
-
   /** Dagger qualifier for the subdirectory we stage to/upload from. */
   @Qualifier
   @Documented

java/google/registry/ui/server/registrar/SendEmailUtils.java

@@ -21,7 +21,6 @@ import com.google.common.base.Joiner;
 import com.google.common.collect.Streams;
 import com.google.common.flogger.FluentLogger;
 import google.registry.config.RegistryConfig.Config;
-import google.registry.util.NonFinalForTesting;
 import google.registry.util.SendEmailService;
 import java.util.List;
 import java.util.Objects;
@@ -39,18 +38,18 @@ public class SendEmailUtils {
 
   private final String gSuiteOutgoingEmailAddress;
   private final String gSuiteOutoingEmailDisplayName;
+  private final SendEmailService emailService;
 
   @Inject
   public SendEmailUtils(
       @Config("gSuiteOutgoingEmailAddress") String gSuiteOutgoingEmailAddress,
-      @Config("gSuiteOutoingEmailDisplayName") String gSuiteOutoingEmailDisplayName) {
+      @Config("gSuiteOutoingEmailDisplayName") String gSuiteOutoingEmailDisplayName,
+      SendEmailService emailService) {
     this.gSuiteOutgoingEmailAddress = gSuiteOutgoingEmailAddress;
     this.gSuiteOutoingEmailDisplayName = gSuiteOutoingEmailDisplayName;
+    this.emailService = emailService;
   }
 
-  @NonFinalForTesting
-  private static SendEmailService emailService = new SendEmailService();
-
   /**
    * Sends an email from Nomulus to the specified recipient(s). Returns true iff sending was
    * successful.

java/google/registry/util/SendEmailService.java

@@ -15,6 +15,8 @@
 package google.registry.util;
 
 import java.util.Properties;
+import javax.inject.Inject;
+import javax.inject.Singleton;
 import javax.mail.Message;
 import javax.mail.MessagingException;
 import javax.mail.Session;
@@ -22,8 +24,12 @@ import javax.mail.Transport;
 import javax.mail.internet.MimeMessage;
 
 /** Wrapper around javax.mail's Transport.send that can be mocked for testing purposes. */
+@Singleton
 public class SendEmailService {
 
+  @Inject
+  SendEmailService() {};
+
   /** Returns a new MimeMessage using default App Engine transport settings. */
   public Message createMessage() {
     return new MimeMessage(Session.getDefaultInstance(new Properties(), null));