chore: import upstream snapshot with attribution

examples/todo application/todo_form.sql

@@ -0,0 +1,33 @@
+
+-- When the form is submitted, we insert the todo item into the database
+-- or update it if it already exists
+-- and redirect the user to the home page.
+-- When the form is initially loaded, :todo is null,
+-- nothing is inserted, and the 'redirect' component is not returned.
+insert or replace into todos(id, title)
+select $todo_id, :todo -- $todo_id will be null if the page is accessed via the 'Add new todo' button (without a ?todo_id= parameter)
+where :todo is not null -- only insert if the form was submitted
+returning
+    'redirect' as component,
+    '/' as link;
+
+-- The header needs to come before the form, but after the potential redirect
+select 'dynamic' as component, sqlpage.run_sql('shell.sql') as properties;
+
+-- The form needs to come AFTER the insert statement
+-- because the insert statement will redirect the user to the home page if the form was submitted
+select 
+    'form'            as component,
+    'Todo'            as title,
+    (
+        case when $todo_id is null then
+            'Add new todo'
+        else
+            'Edit todo'
+        end
+    ) as validate;
+select 
+    'Todo item' as label,
+    'todo' as name,
+    'What do you have to do ?' as placeholder,
+    (select title from todos where id = $todo_id) as value;