refactoring: move sql files

resources/sql/functions/article/find_article_by_id.sql

@@ -0,0 +1,18 @@
+create or replace function find_article_by_id(in id uuid, out resource json) language plpgsql as
+$$
+declare
+    _id alias for id;
+begin
+    select to_json(t)
+    from (
+        select
+            a.*,
+            find_citizen_by_id(a.created_by_id) as created_by
+        into resource
+        from article as a
+        where a.id = _id
+    ) as t;
+end;
+$$;
+
+-- drop function if exists find_article_by_id(uuid, out json);