title: Provide extra information to Flask's app.logger
body: <p>The <a href="http://flask.pocoo.org/docs/0.10/api/#flask.Flask.debug_log_format" rel="noreferrer">default debug log format</a> for Flask 0.10 is</p>
  
  <pre><code>debug_log_format =
  '-------------------------------------------------------------------------\n%
  %(levelname)s in %(module)s [%(pathname)s:%(lineno)d]:\n%(message)s
  \n-------------------------------------------------------------------------'
  </code></pre>
  
  <p>How do I change it to this:</p>
  
  <pre><code>'-------------------------------------------------------------------------\n%
  work_id %(levelname)s in %(module)s [%(pathname)s:%(lineno)d]:\n%(message)s
  \n-------------------------------------------------------------------------'
  </code></pre>
  
  <p>where <code>work_id</code> is a randomly generated UUID for each request.</p>
  
  <p>If the logger is created by myself, I can just use a <code>logging.LoggerAdapter</code> and provide the extra information as a dict <code>{'work_id': some_uuid}</code>, then I can access it in the log record using <code>record.work_id</code>.</p>
  
  <p>But the <code>app.logger</code> is created by <a href="https://github.com/mitsuhiko/flask/blob/33534bb4a9937e6faba5ecec4586519f453369b6/flask/logging.py#L50" rel="noreferrer"><code>create_logger()</code> in Flask's<code>logging.py</code></a>, do I have to modify the Flask source to achieve what I want?</p>
  
  <p>I also thought just override <code>app.logger</code> with my own logger, like <code>app.logger = my_logger</code>, it doesn't seem right.</p>