Change @Auth to an AutoValue, and created a set of predefined Auths

We want to be safer and more explicit about the authentication needed by the many actions that exist.

As such, we make the 'auth' parameter required in @Action (so it's always clear who can run a specific action) and we replace the @Auth with an enum so that only pre-approved configurations that are aptly named and documented can be used.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=162210306

java/google/registry/backup/CommitLogCheckpointAction.java

@@ -26,6 +26,7 @@ import com.googlecode.objectify.VoidWork;
 import google.registry.model.ofy.CommitLogCheckpoint;
 import google.registry.model.ofy.CommitLogCheckpointRoot;
 import google.registry.request.Action;
+import google.registry.request.auth.Auth;
 import google.registry.util.Clock;
 import google.registry.util.FormattingLogger;
 import google.registry.util.TaskEnqueuer;
@@ -43,9 +44,11 @@ import org.joda.time.DateTime;
  * <p>This action's supported method is GET rather than POST because it gets invoked via cron.
  */
 @Action(
-    path = "/_dr/cron/commitLogCheckpoint",
-    method = Action.Method.GET,
-    automaticallyPrintOk = true)
+  path = "/_dr/cron/commitLogCheckpoint",
+  method = Action.Method.GET,
+  automaticallyPrintOk = true,
+  auth = Auth.AUTH_INTERNAL_ONLY
+)
 public final class CommitLogCheckpointAction implements Runnable {
 
   private static final FormattingLogger logger = getLoggerForCallerClass();