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/export/UpdateSnapshotViewAction.java

@@ -13,6 +13,7 @@
 // limitations under the License.
 
 package google.registry.export;
+
 import static google.registry.request.Action.Method.POST;
 
 import com.google.api.client.googleapis.json.GoogleJsonResponseException;
@@ -27,13 +28,18 @@ import google.registry.config.RegistryConfig.Config;
 import google.registry.request.Action;
 import google.registry.request.HttpException.InternalServerErrorException;
 import google.registry.request.Parameter;
+import google.registry.request.auth.Auth;
 import google.registry.util.FormattingLogger;
 import google.registry.util.SqlTemplate;
 import java.io.IOException;
 import javax.inject.Inject;
 
 /** Update a well-known view to point at a certain Datastore snapshot table in BigQuery. */
-@Action(path = UpdateSnapshotViewAction.PATH, method = POST)
+@Action(
+  path = UpdateSnapshotViewAction.PATH,
+  method = POST,
+  auth = Auth.AUTH_INTERNAL_ONLY
+)
 public class UpdateSnapshotViewAction implements Runnable {
 
   /** Headers for passing parameters into the servlet. */