Set svID in ConfigModule instead of hard-coding it

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=138552819

java/google/registry/config/ConfigModule.java

@@ -863,4 +863,15 @@ public final class ConfigModule {
   public static Duration provideAsyncDeleteFlowMapreduceDelay() {
     return Duration.standardSeconds(90);
   }
+
+  /**
+   * The server ID used in the 'svID' element of an EPP 'greeting'.
+   *
+   * @see <a href="https://tools.ietf.org/html/rfc5730">RFC 7530</a>
+   */
+  @Provides
+  @Config("greetingServerId")
+  public static String provideGreetingServerId() {
+    return "Charleston Road Registry";
+  }
 }

java/google/registry/flows/session/HelloFlow.java

@@ -14,6 +14,7 @@
 
 package google.registry.flows.session;
 
+import google.registry.config.ConfigModule.Config;
 import google.registry.flows.EppException;
 import google.registry.flows.ExtensionManager;
 import google.registry.flows.Flow;
@@ -26,11 +27,12 @@ public class HelloFlow implements Flow {
 
   @Inject ExtensionManager extensionManager;
   @Inject Clock clock;
+  @Inject @Config("greetingServerId") String greetingServerId;
   @Inject HelloFlow() {}
 
   @Override
   public Greeting run() throws EppException {
     extensionManager.validate();  // There are no legal extensions for this flow.
-    return Greeting.create(clock.nowUtc());
+    return Greeting.create(clock.nowUtc(), greetingServerId);
   }
 }

java/google/registry/model/eppoutput/Greeting.java

@@ -31,7 +31,7 @@ import org.joda.time.DateTime;
  */
 public class Greeting extends ImmutableObject implements ResponseOrGreeting {
 
-  String svID = "Charleston Road Registry";
+  String svID;
   DateTime svDate;
 
   /** This is never changed, so it might as well be static for efficiency. */
@@ -42,8 +42,9 @@ public class Greeting extends ImmutableObject implements ResponseOrGreeting {
   @XmlElement
   static Dcp dcp = new Dcp();
 
-  public static Greeting create(DateTime svDate) {
+  public static Greeting create(DateTime svDate, String svID) {
     Greeting instance = new Greeting();
+    instance.svID = svID;
     instance.svDate = svDate;
     return instance;
   }