Translation takes place after the content of a book is finalized, at a point where authors may not know who (if anybody) will translate the book. A per-language XML file could hold a <othercredit class="translator"> element to include in the front matter of translated books, and would allow translators to set this credit appropriately for their language.
Added handling of $translation/Author_Group.xml, when a book is built this file, if it exists, will be appended to the $source_lang/Author_Group.xml file. $translation/Author_Group.xml and $source_lang/Author_Group.xml must both be a valid DocBook authorgroups.
create book with at least 1 translation set up for it. then add an author group xml file to the translation directory. build and verify that the translated author xml gets added to the english xml. 1 hour.
Verified, works beautifully. Translator's credits are added underneath the writer's credits, see attached screenshot if anyone's interested.
Created attachment 591732 [details] Writers and Translators Credits
Documentation might be needed for adding translator credit.