Re-write fhir services to factory

[ruscoder]

Currently, we have some issues with working with base fhir services, since URL, token, and inactiveMapping are defined globally:

• All service functions hardly tied to the single global base URL/token
• Impossible to override inactiveMapping

The better approach is to define them in a factory function, that will return new AidboxClient class that will have all methods from services/fhir.ts (e.g. getFHIRResources, saveFHIRResource and etc).