title: ActiveStorage Uploading to S3 with original file extension
body: <p>I am uploading APK files to Amazon S3 via Rails ActiveStorage.
  The upload is working fine, but when I try to retrieve the files, download them, I see that file extensions and content types are changed. </p>
  
  <p>The APK files are being downloaded as ZIP files.</p>
  
  <p>I know that ActiveStorage does work on the files and identify their content type, but in my case it simply cannot identify. </p>
  
  <p>I need ActiveStorage to not to handle extension or content-type, just move the file into the cloud.</p>
  
  <p>I have configured ActiveStorage to work with S3 and attaching files by:</p>
  
  <pre><code>instance.attach(io: File.open('VALID_FILE_PATH_HERE'), filename: 'filename.apk')
  </code></pre>
  
  <p>I also tried providing</p>
  
  <pre><code>content_type: "application/vnd.android.package-archive"
  </code></pre>
  
  <p>But it did not change anything, and when I append</p>
  
  <pre><code>identify: false
  </code></pre>
  
  <p>It throws an exception, saying unexpected key for identify.</p>
  
  <p>Is there a way to make ActiveStorage simply move the file as it is?</p>