Add a Recipe to the grocery list. In the request data, pass in recipeId, scale (scale=1.0 says to keep the recipe the same size as originally posted), markAsPending (true/false) to indicate that the lines in the recipe should be marked in a "pending" (unconfirmed by user) state.

{
  "type": "object",
  "properties": {
    "markAsPending": {
      "type": "boolean",
      "description": "Gets or sets the mark as pending."
    },
    "recipeId": {
      "type": "integer",
      "format": "int32",
      "description": "Gets or sets the recipe identifier."
    },
    "scale": {
      "type": "number",
      "format": "double",
      "description": "Gets or sets the scale."
    }
  }
}