Create a new document metadata record for a caregiver.

IMPORTANT: This endpoint creates METADATA only.

• ✓ Records document name, type, status, expiry/effective dates
• ❌ Does NOT accept the file binary itself
• ❌ Does NOT upload to S3

File binary upload is not currently available via the public API. The
actual document file should be uploaded to Viv via another channel
(e.g. office portal); this endpoint only registers the corresponding
metadata entry on the caregiver record.

About type: the type field is a tenant-configured string label.
Valid values are the caregiver document types set up by the customer's
org admin in Viv (Settings → Caregiver Document Types), aggregated
across the caregiver's geo and all predecessor geos. The fallback
type "Not provided" is also accepted (it maps to the UI's untyped
document group). Matching is case-sensitive and exact.

On invalid types the API returns 400 INVALID_DOCUMENT_TYPE and
the response includes the full list of valid types in
details.validTypes so callers can self-correct without a separate
lookup. Coordinate with the org admin to enumerate the list ahead of
time — there is currently no public-API endpoint that returns it.