def update
      if @comment.update(params.permit(:content))
        render json: @comment
      else
        render json: @comment.errors, status: 422
      end
    end
def update
      if @comment.update(params.permit(:content))
        render json: @comment
      else
        render json: @comment.errors, status: 422
      end
    end
Updates a comment

 `PUT /api/boards/:board_id/posts/:post_id/comments/:id`