public static String getDatabaseKey( Plugin plugin )
    {
        return getDatabaseKey( XMPPServer.getInstance().getPluginManager().getPluginPath( plugin ) );
    }
Returns the database schema key of a plugin, if it exists. The value is retrieved from the plugin.xml file of the
plugin. If the value could not be found, {@code null} will be returned.

Note that this method will return data only for plugins that have successfully been installed. To obtain data
from plugin (directories) that have not (yet) been  installed, refer to the overloaded method that takes a Path
argument.

@param plugin The plugin (cannot be null)
@return the plugin's database schema key or {@code null} if it doesn't exist.
xmppserver/src/main/java/org/jivesoftware/openfire/container/PluginMetadataHelper.java