Adjust fhir-py to work with any models

[ruscoder]

Currently fhirpy is limited to work with pydantic models that matches Resource interface.

In addition to it, it expects defining resourceType with typehint that is a bit dirty.

I suggest using class name as resource type instead of trying to get it from the resource model, but in that case, resource class names must match the resource type.

[ruscoder]

List of models:

• https://github.com/beda-software/fhir-py-types-r4b
• https://github.com/fhir-schema/fhir-schema-codegen/tree/main/example/python/aidbox
• https://github.com/smart-on-fhir/client-py/blob/main/fhirclient/models/