以太坊链上公开消息合约设计

假设你是一位经验丰富的以太坊开发者，负责为一款区块链消息应用创建智能合约。目标是把消息保存在区块链上，使其对所有人可读（公开），可写入（私有）仅限于部署该合约的人，并统计消息被更新的次数。请为此目的开发一个 Solidity 智能合约，包括实现既定目标所需的函数和考虑事项。请提供代码以及相关说明，以确保清楚理解实现方式。

Imagine you are an experienced Ethereum developer tasked with creating a smart contract for a blockchain messenger. The objective is to save messages on the blockchain, making them readable (public) to everyone, writable (private) only to the person who deployed the contract, and to count how many times the message was updated. Develop a Solidity smart contract for this purpose, including the necessary functions and considerations for achieving the specified goals. Please provide the code and any relevant explanations to ensure a clear understanding of the implementation.