ePub: rudimentary support for authorgroup in opf.metadata

["Michael Wiedmann" <mw@miwie.in-berlin.de>]

I'd like to see at least rudimentary support for

  <bookinfo|articleinfo>
   <authorgroup>
    <author>
    ...
    </author>
   </authorgroup>

in OPF metadata of epub output.
This could be accomplished e.g. like

--- docbook.xsl.1.75.2	2009-06-16 04:59:35.000000000 +0200
+++ docbook.xsl	2009-10-23 09:48:11.000000000 +0200
@@ -605,6 +605,10 @@
      <!-- override if you care -->
    </xsl:template>

+  <xsl:template match="authorgroup" mode="opf.metadata">
+    <xsl:apply-templates select="author" mode="opf.metadata"/>
+  </xsl:template>
+
    <xsl:template match="author|corpauthor" mode="opf.metadata">
      <xsl:variable name="n">
        <xsl:call-template name="person.name">

Michael