adding created_at to the event metadata

Author: AlexandreDecollas

src/dto/event-metadata.dto.ts

@@ -1,5 +1,6 @@
 import {
   Equals,
+  IsDate,
   IsNotEmpty,
   IsOptional,
   IsPositive,
@@ -92,4 +93,11 @@ export class EventMetadataDto {
   @IsString()
   @IsNotEmpty()
   correlation_id: string;
+
+  /**
+   * Business process unique id
+   * @example 15d5f8d5-869e-4107-9961-5035495fe416
+   */
+  @IsDate()
+  created_at?: string;
 }