title: How do you set "Content-Type" when saving to S3 using django-storages with S3boto backend?
body: <p>I am using <code>django-storages</code> with <code>s3boto</code> as a backend.</p>
  
  <p>I have one bucket with two folders - one for <code>static</code> and one for <code>media</code>.  I achieve this using <code>django-s3-folder-storage</code>.</p>
  
  <p>As well as saving to S3 using a model, I also want to implement an image-resize-and-cache function to save the files to S3.  To do this I interact directly with my S3 bucket.  The code works, but the <code>Content-Type</code> isn't set on S3.</p>
  
  <p>in iPython:</p>
  
  <pre><code>In [2]: from s3_folder_storage.s3 import DefaultStorage
  
  In [3]: s3media = DefaultStorage()
  
  In [4]: s3media
  Out[4]: &lt;s3_folder_storage.s3.DefaultStorage at 0x4788780&gt;
  </code></pre>
  
  <p>Test we're accessing the right bucket - <code>storage_test</code> is one I created earlier:</p>
  
  <pre><code>In [5]: s3media.exists('storage_test')
  Out[5]: True
  
  In [6]: s3media.open("test.txt", "w")
  Out[6]: &lt;S3BotoStorageFile: test.txt&gt;
  
  In [7]: test = s3media.open("test.txt", "w")
  
  In [8]: test
  Out[8]: &lt;S3BotoStorageFile: test.txt&gt;
  
  In [9]: test.key.content_type = "text/plain"
  
  In [10]: test.write("...")
  
  In [11]: test.close()
  
  In [12]: test = s3media.open("test.txt", "w")
  
  In [13]: test.key.content_type
  Out[13]: 'binary/octet-stream'
  </code></pre>
  
  <p>I've also tried instead of <code>In [9]</code> using <code>test.key.metadata</code> and <code>test.key.set_metadata</code>.  None of them do it.</p>
  
  <p>How do I set the correct Content-Type?</p>