Callbacks service docs updated

interface/models/storable.yaml

@@ -1,6 +1,7 @@
 components:
   schemas:
     Storable:
+      description: Common persistence metadata included on stored entities.
       type: object
       additionalProperties: false
       required:
@@ -9,10 +10,13 @@ components:
         - updatedAt
       properties:
         id:
+          description: Unique identifier assigned to the stored entity.
           $ref: ./objectid.yaml#/components/schemas/ObjectId
         createdAt:
+          description: RFC 3339 timestamp indicating when the entity was created.
           type: string
           format: date-time
         updatedAt:
+          description: RFC 3339 timestamp indicating the most recent entity update.
           type: string
           format: date-time