message: Add 404 for HEAD APIs.
diff: "204": {
  "description": "No Content"
  },
  + "404": {
  + "description": "Not Found"
  + },
  "default": {
  "description": "Error response describing why the operation failed.",
  "schema": {
  "204": {
  "description": "No Content"
  },
  + "404": {
  + "description": "Not Found"
  + },
  "default": {
  "description": "Error response describing why the operation failed.",
  "schema": {
  "204": {
  "description": "No Content"
  },
  + "404": {
  + "description": "Not Found"
  + },
  "default": {
  "description": "Error response describing why the operation failed.",
  "schema": {
  "204": {
  "description": "No Content"
  },
  + "404": {
  + "description": "Not Found"
  + },
  "default": {
  "description": "Error response describing why the operation failed.",
  "schema": {
  "204": {
  "description": "No Content"
  },
  + "404": {
  + "description": "Not Found"
  + },
  "default": {
  "description": "Error response describing why the operation failed.",
  "schema": {
  "204": {
  "description": "No Content"
  },
  + "404": {
  + "description": "Not Found"
  + },
  "default": {
  "description": "Error response describing why the operation failed.",
  "schema": {
  "204": {
  "description": "No Content"
  },
  + "404": {
  + "description": "Not Found"
  + },
  "default": {
  "description": "Error response describing why the operation failed.",
  "schema": {
  "204": {
  "description": "No Content"
  },
  + "404": {
  + "description": "Not Found"
  + },
  "default": {
  "description": "Error response describing why the operation failed.",
  "schema": {
  