Enhance deidentified resources with information about removed (deidentified) paths

[philwinn]

For a user of deidentified FHIR resources, it might be important to know which paths were removed (deidentified) by the deidentification process. Unless this information is not encoded as part of a deidentified resource, it is impossible for a user to know whether a particular data point is simply missing in the original resource or was removed by the deidentification process.

This enhancement could be implemented as either

• an Extension that lists all deidentified paths or
• Tags (searchable!) that encode the deidentified paths

[tobiasgirardet]

One drawback I can think about is that this information might expose an additional "attack surface" for re-identification of a patient. Therefore, this should be an optional feature, that is disabled by default.