Extension helpers: `<ResourceType>ExtensionProfile`

[ryukzak]

For each ResourceType, we can find applicable extensions (context https://build.fhir.org/defining-extensions.html#context field in the extension SD). This allows us to generate an artificial profile, which will provide a nice and easy way to get and set applicable extensions. Let's see how it works with a regular profile (https://build.fhir.org/ig/HL7/US-Core/StructureDefinition-us-core-patient.html and https://build.fhir.org/ig/HL7/US-Core/StructureDefinition-us-core-race.profile.json.html):

const patient = { resourceType: "Patient" };
const patientProfile = new USCorePatientProfileProfile(patient);

patientProfile
    .setRace({
        ombCategory: {
            system: "urn:oid:2.16.840.1.113883.6.238",
            code: "2106-3",
            display: "White",
        },
        text: "White",
    })

We can automatically generate the same thing for arbitrary extensions without any additional constraints.

const patient = { resourceType: "Patient" };
const patientExtensions = new PatientExtensionProfile(patient);

patientExtensions
    .setRace({
        ombCategory: {
            system: "urn:oid:2.16.840.1.113883.6.238",
            code: "2106-3",
            display: "White",
        },
        text: "White",
    })

Artificial profiles should work very well because they can be performed at the TypeSchema level, so they will automatically provide support for all generators that support profiles.

Open problems:

• Extension name: by default we can get sd.name, but in case of name collisions or GUID-like strings, we can extract it from the URL, etc.
  • Provide the user control over extension naming as part of generator configuration.
• Number of applicable extensions:
  • Explicitly configure extensions related to ResourceType
  • Limit the maximum number of extensions in <ResourceType>ExtensionProfile
• Inheritance in sd.context which can be applicable for any element:
  • https://build.fhir.org/ig/HL7/fhir-extensions/StructureDefinition-data-absent-reason.html
• Primitive type and Element extensions