Make attestation-only commit require a Contribution
Currently the semantics of the common.change_control package allow for attestations to be added to Versions, without a Contribution being required. This should be changed to ensure that any change whatsoever to the EHR has a Contribution.
- change text in change_control package to indicate that Contributions are always
required, including for attestation-only commits, and that the Contribution.
audit_details.change_type will be set to the new code 'attestation'
- change Contribution class definition to indicate that the versions list in the
case of an attestation is just the list of versions being attested.
- add a new code to the terminology value set 'audit change type' for 'attestation'.