Support for non-integer IDs

[LJNIC]

OMOP-on-FHIR assumes FHIR resources will have numeric IDs, but FHIR resources can have other characters. Our FHIR EHR uses UUIDs, which we'd like to convert to OMOP for use with OHDSI tools.

[myungchoi]

In this case, we need to have a mapping table that maps UUIDs to/from Integer. I tried to do this but didn't have time and fund to do that. In some of code, I had mapping class, which currently returns the same numeric id. This can be used to implement the mapping from mapping table in the database (requires to create a new table.). I suggest you to create f_id_mapping table so that we can keep the naming convention. If you can contribute this, it will be a great addition to the OMOPonFHIR community.