patientId property
https://build.fhir.org/ig/HL7/smart-app-launch/scopes-and-launch-context.html#launch-context-arrives-with-your-access_token Once an app is authorized, the token response will include any context data the app requested and any (potentially) unsolicited context data the EHR may decide to communicate. For example, EHRs may use launch context to communicate UX and UI expectations to the app (see need_patient_banner below).
String value with a patient id, indicating that the app was launched in the context of FHIR Patient 123. If the app has any patient-level scopes, they will be scoped to Patient 123.
Implementation
String? patientId;