title: Serilog.Extras.AppSettings and complex objects
body: <p>I'm using the Serilog.Extras.AppSetting package, to configure Serilog. I'm attempting to use the Email sink (Serilog.Sinks.Email), but I can't figure out how to configure the network credentials property via an AppSetting.</p>
  
  <pre><code>    &lt;add key="serilog:using" value="Serilog.Sinks.Email" /&gt;
      &lt;add key="serilog:write-to:Email.mailServer" value="localhost" /&gt;
      &lt;add key="serilog:write-to:Email.fromEmail" value="test@google.com" /&gt;
      &lt;add key="serilog:write-to:Email.toEmail" value="test@google.com" /&gt;
      &lt;add key="serilog:write-to:Email.restrictedToMinimumLevel " value="Error" /&gt;
  
  &lt;add key="serilog:write-to:Email.networkCredential" value="???" /&gt;
  </code></pre>
  
  <p>How can I specify/represent an <em>NetworkCredential</em> object using AppSettings? Is it even possible, or is this a limitation of the AppSetting approach to configuration in Serilog?</p>