Handle json payload configurations

[Wambere]

Related to #235

The initial plan was that any of the system urls (more than for locations) might need to change based on the project/implementation (maybe even the whole json object sometimes?), and that these would just be changed on the json payloads when working with the different projects to avoid the the configuration and implementation being too long and maybe confusing. So kind of thinking of the json payloads as "part of" the configuration.

However, we now have the FHIR web bulk uploader functionality that needs to work with this

So the task here is to figure out how best to make this work