message: refine description of the etag
diff: },
  "ETag": {
  "type": "object",
  - "description": "Entity tag is used for comparing two or more entities from the same requested resource. ETags may be returned for individual resources, and then sent via If-Match / If-None-Match headers for concurrency control. ",
  + "description": "Entity tag is used for comparing two or more entities from the same requested resource.",
  "properties": {
  "etag": {
  "type": "string",
  - "description": "Entity tag is used for comparing two or more entities from the same requested resource. ETags may be returned for individual resources, and then sent via If-Match / If-None-Match headers for concurrency control. "
  + "description": "Entity tag is used for comparing two or more entities from the same requested resource."
  }
  }
  },
  