Add support for $validate-code

[CaitlinV39]

User story
I want to validate the snomed code in .net core, how can i use "$validate-code" command in .net core for Azure API for FHIR

https://docs.microsoft.com/en-us/answers/questions/601649/index.html

Acceptance criteria
Can use $validate-code

[CaitlinV39]

AB#85022