Update conversion data types

IMPORTANT: Where possible all PRs must be linked to a Github issue

Fixes #[issue number] or Closes #[issue number]

Engineer Checklist

[ ] I have run mvn spotless:apply to check my code follows the project's style guide
[ ] I have built and run the efsity jar to verify my change fixes the issue and/or does not break the application

onaio / fhir-tooling