Make sure all DoFns are idempotent

[bashir2]

One of the requirements of a DoFn in the Beam model is idempotence. There are places in the code that we are breaking this rule, for example this TODO which can cause the same FHIR resource being written into Parquet files multiple times.

Another possible example is when we write resources into another FHIR server. We should make sure that updating the same resources multiple times is properly handled.

This tracking issue is to check/fix all potential idempotent issues.