Update medication resource type to have native terminology type code as well as generic code

[dionmcm]

Expected behaviour

• Medication type should supply multiple codings including the native coding (e.g. AMT code for MPP as well as the generic coding which is cross terminology)

Actual behaviour

• Only the generic cross terminology code is available

Note

This will be a breaking change as it will take the extension from Coding to List or CodableConcept