Add helper methods to DatastoreAdmin Operation object

These are needed by Datastore export management actions.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=224242281

java/google/registry/export/datastore/BUILD

@@ -9,10 +9,13 @@ java_library(
     srcs = glob(["*.java"]),
     deps = [
         "//java/google/registry/config",
+        "//java/google/registry/util",
         "@com_google_api_client",
+        "@com_google_code_findbugs_jsr305",
         "@com_google_dagger",
         "@com_google_guava",
         "@com_google_http_client",
         "@com_google_http_client_jackson2",
+        "@joda_time",
     ],
 )