The management API could only upsert a material on its title and course,
so a renamed note became a second material. PUT /materials/{id} applies the
same body to one material (422 when the new title and course belong to
another one), GET /materials/{id} shows a draft or published material with
its public files, and the upsert, update and validation share one path.
The README documents the management API.
Datepickers on native time.Time / lagoon.Date fields, file uploads on
materials, readings and class sessions managed from the course form
(course_id made nullable).
Overview, features, the API reference with every route and response
shape, admin screens, configuration, the bm:seed file format,
dependencies and testing.
