Create or update a practitioner-group association

Creates or updates the association between a practitioner and a group as an upsert: if the practitioner is already associated with the group the existing association is updated, otherwise a new association is created. The request body is validated against the TenantGroupPractitioner schema before persistence. Use this when enrolling a practitioner in a group or updating group-level association attributes; note that this operation uses PUT with upsert semantics, so it returns 200 (not 201) even when creating a new association. {practitionerId} is the certifyPractitionerId, {groupId} is the group identifier, and the request body must conform to the TenantGroupPractitioner schema.