Change LaunchAgent to LaunchDaemon

Question

I have a Homebrew MYSQL install on a Lion Mac Computer.

Now I want Mysql to start even if the user is not signed in. Can I now simply copy the LaunchAgent .plist file to the LaunchDaemons folder. So assuming this is possible, then the next question is, what the user name should be in the plist file.

This is the plist file:

<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
  <key>KeepAlive</key>
  <true/>
  <key>Label</key>
  <string>homebrew.mxcl.mysql</string>
  <key>Program</key>
  <string>/usr/local/bin/mysqld_safe</string>
  <key>RunAtLoad</key>
  <true/>
  <key>UserName</key>
  <string>??????????????????????????????????????????????????</string>
  <key>WorkingDirectory</key>
  <string>/usr/local/var</string>
</dict>
</plist>