title: what is the difference getContentMd5() and getETag() of aws s3 PutObjectResult
body: <p><code>getEtag()</code> seems to return base64 encoded md5. So what does <code>getContentMd5</code> return? How are they related?</p>
  
  <p><strong>One example:</strong></p>
  
  <pre><code> getContentMd5() -&gt; /yoLi66uT7Q6qaverVTqrQ==
   getEtag() -&gt; ff2a0b8baeae4fb43aa9abdead54eaad
  </code></pre>