[dossier] Add usage (code and text) to medications

schemas/med_dossier/Medication.yaml

@@ -55,3 +55,14 @@ properties:
       *OPTIONAL* If automatically sent to a specific pharmacy, some source-system custom coding that indicates which pharmacy it was sent to.
     type: string
     example: AN
+  usageCode:
+    description: |-
+      *OPTIONAL* A coded description of how to use this medication. Depends on source HIS software; sometimes even on the individual configuration of
+      a practice's HIS or that practice's regional server; these values aren't normalized, and sometimes not available at all.
+    type: string
+    example: 1D1T
+  usageText:
+    description: |-
+      *OPTIONAL* Human-readable (dutch) description of how to use this medication. Depends on source HIS software and often not available at all.
+    type: string
+    example: Gebruik bekend