Add discovery service to stable APIs

generated/googleapis/test/admin/email_migration_v2_test.dart

 library googleapis.admin.email_migration_v2.test;
 
 import "dart:core" as core;
 import "dart:collection" as collection;
 import "dart:async" as async;
 import "dart:convert" as convert;
 
 import 'package:http/http.dart' as http;
 import 'package:http/testing.dart' as http_testing;
 import 'package:unittest/unittest.dart' as unittest;
@@ skipping 116 matching lines @@
         return new async.Future.value(common_test.stringResponse(200, h, resp));
       }), true);
       res.insert(arg_request, arg_userKey).then(unittest.expectAsync((_) {}));
     });
 
   });
 
 
 }