refactor(server): mail service (#10934)

packages/backend/server/src/base/job/queue/def.ts

@@ -63,3 +63,7 @@ If you want to introduce new job queue, please modify the Queue enum first in ${
 export function getJobHandlerMetadata(target: any): JobName[] {
   return sliceMetadata<JobName>(JOB_METADATA, target);
 }
+
+export enum JOB_SIGNAL {
+  RETRY = 'retry',
+}