[SPIKE] Review FHIR Converter Logic with respect to the bulk upload API

[DanielSass]

Related to #7897, #7898 and #7804

We've run into a couple issues now stemming from users of the bulk upload using SNOMED codes for test results that are different from what the single entry flow uses. The core issue here is that the FHIR converter logic does not appropriately handle the values that are possible in the bulk uploader (and thus have some bad default values that are causing issues downstream).

The request for this spike is to investigate all of the FHIR mappings specifically with respect to the inputs that are allowed / recommended by the bulk upload guide (and subsequently how we translate those values through the bulk result upload validation and mapping flow).

[mehansen]

I would also look out for whether the bulk upload guide accurately reflects the validations for each field because sometimes I think it's out of sync