Implement a CDS Hooks patient-view service that fires when a patient chart opens, returns information cards with relevant gap-in-care alerts, and handles the prefetch template to avoid extra server round-trips

Steps

1. Register the service at /.well-known/cds-services with hook: patient-view and declare a prefetch template for Patient and Condition
2. Accept the CDS Hooks request body (hook, hookInstance, context.patientId, prefetch) and validate the JWT bearer token from the EHR
3. Evaluate the prefetched data against care gap rules and build Card objects with summary, detail, indicator, and source fields
4. Return a JSON response with a cards array; omit the suggestions array when no actionable suggestion applies
5. Handle the case where prefetch data is absent by fetching the FHIR resources directly using the fhirAuthorization token
6. Return an empty cards array rather than an error when no gaps are found to avoid alert fatigue