Add extra flow logic hooks for info and update

This CL adds the hooks necessary to implement TLD-specific flow info and update flow logic. Usage of the hooks follows in a separate CL.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=130108832

java/google/registry/model/domain/flags/FlagsList.java

@@ -24,4 +24,8 @@ import javax.xml.bind.annotation.XmlElement;
 public class FlagsList {
   @XmlElement(name = "flag")
   List<String> flags;
+
+  public List<String> getFlags() {
+    return flags;
+  }
 }