[api] Clarified doctor codes in population API's.

zoo-api.yaml

@@ -148,6 +148,15 @@ components:
       required: false
       schema:
         type: string
+    DoctorCodes:
+      name: doctorCodes
+      in: query
+      description: Code of the doctor as known in the HIS.
+      example: AA,BZP,RZ,ECH
+      schema: 
+        type: array
+        items: 
+          $ref: schemas/med_dossier/Practitioner.yaml
   responses:
     ReqFailure:
       description: The request isn't valid; for example, it is missing a required parameter.