Set termination date on a single practitioner role assignment

Sets the terminationDate on a single role entry within a practitioner's location-network assignment. This operation is scoped to a single role in a single assignment and does not cascade to any parent records — the location-network assignment itself, the network participation record, or the practitioner's main termination status. Use it when a specific role held at a particular location-network pairing has ended but the practitioner's other roles and assignments remain active; for practitioner-wide termination, use PUT /practitioners/terminate instead. {id} is the location-network assignment (TGLPN) identifier obtained from the practitioner's relationship data, and the target role key must exist within that assignment; if the role's stored effectiveDate cannot be parsed as a valid ISO date, the termination-before-effective constraint is skipped and the request succeeds as a legacy-record accommodation.