feature #4: add "article in title" on contitution creation

resources/functions/constitution/create_title_in_constitution.sql

@@ -0,0 +1,35 @@
+create or replace function create_title_in_constitution(title json, constitution_id uuid default null, out resource json)
+    language plpgsql as
+$$
+declare
+    _title alias for title;
+    _constitution_id uuid = coalesce(constitution_id, (title#>>'{constitution_id}')::uuid);
+    _author_id uuid = (title#>>'{created_by, id}')::uuid;
+    new_id uuid;
+begin
+    insert into title (created_by_id, name, rank, constitution_id)
+    select
+        _author_id,
+        ti.name,
+        row_number() OVER (),
+        _constitution_id
+    from json_populate_record(null::title, _title) ti
+    returning id into new_id;
+
+    if (_title->'articles' is not null) then
+        insert into article_in_title (created_by_id, rank, title_id, article_id, constitution_id)
+        select
+            _author_id,
+            row_number() over (),
+            new_id,
+            id,
+            coalesce ((_title->>'constitution_id')::uuid, _constitution_id)
+        from json_populate_recordset(null::article, _title->'articles') ;
+    end if;
+
+    select find_constitution_title_by_id(new_id)
+    into resource;
+end;
+$$;
+
+-- drop function if exists create_title_in_constitution(out json);