Create courses

Create up to BATCH_MAX_ITEMS courses in a single request.

Returns 200 if all items succeed, 207 if any fail, 400 if the envelope is empty or over the cap. Per-row failures (unresolved created_by_email, unhandled exceptions) do not abort the batch.

No within-batch deduplication is applied — Course has no natural uniqueness key like the student-email constraint that drives the students endpoint's first-wins dedup pass.

Required OAuth scope: courses:write