[NTG-context] Combine \setupdelimitedtext with an author (define custom variable?)

Hi,

I like to achieve something that looks like this: ``` \definedelimitedtext[extract][blockquote] \setupdelimitedtext [extract] [leftmargin=1.5pc, style={\italic}, before={\setupindenting[next]}, after={\blank[1ex] \hrule \blank[1ex] \startalignment[flushright] \tfx\italic{René Descartes} \stopalignment}]

\starttext \startextract Cogito ergo sum. \stopextract \stoptext ```

So it should setup a quotation and mentions the author. However, here the author is hardcoded within the blockquote. I would like it to use like this: ``` \definedelimitedtext[extract][blockquote] \setupdelimitedtext [extract] [leftmargin=1.5pc, style={\italic}, before={\setupindenting[next]}, after={\blank[1ex] \hrule \blank[1ex] \startalignment[flushright] \tfx\italic{\getcustomvariable{author}} \stopalignment}]

\starttext \startextract[author=René Descartes] Cogito ergo sum. \stopextract \stoptext ```

Is there an easy way to achieve that? I tried with \structureuservariable (like possible in \startchapter) but it does not work.

Best, Gerion