feature #4: add relations to upsert_article

resources/functions/article/upsert_article.sql

@@ -16,6 +16,15 @@ begin
     from json_populate_record(null::article, resource)
     returning id into new_id;
 
+    if resource->>'relations' is not null then
+        insert into article_relations (source_id, target_id, created_by_id)
+        select
+            (resource->>'id')::uuid,
+            id,
+            (resource#>>'{created_by, id}')::uuid
+        from json_populate_recordset(null::article, resource->>'relations');
+    end if;
+
     select find_article_by_id(new_id) into resource;
 end;
 $$;