public static Version getMinServerVersion( Plugin plugin )
    {
        return getMinServerVersion( XMPPServer.getInstance().getPluginManager().getPluginPath( plugin ) );
    }
Returns the minimum server version this plugin can run within. 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 minimum server version (possibly null).
xmppserver/src/main/java/org/jivesoftware/openfire/container/PluginMetadataHelper.java