Proposal: Make Encounter.reason more versatile by making it a backbone element with a type (CodeableConcept) (Example values: admit-reason, discharge-reason, emergency-reason) and allow references to administrative Resources (Location|Organization)

Encounter
-reason 0..*
-type (CodeableConcept) 0..1
-code (CodeableConcept) 0..1
-reference (Condition | Procedure | Observation | ImmunizationRecommendation | Organization | Location)

This allowes to express things like
* "Reason for Admission: Patient was admitted from care facility X"
(type=admit-reason, code="transfer from external facility", reference=CareFacilityX)
* "Reason for discarge: Patient was discharged to rehab clinic X "
(type=discharge-reason, code="tranfer to external facility", reference=RehabClinicX)
* "Reason for admission: elective surgery of Procedure X"
(type=admit-reason, code=elective procedure, reference=ProcedureX
* "Reason for discharge: Death due to Diagnosis X"
(type=discharge.reason, code=death, reference=Condition X"

The elements
- Encounter.hospitalization.origin
- Encounter.hospitalization.destination
- Encounterhospitalization.dischargeDisposition
would be redundant as they can easily be represented as admission/discharge reasons

Also, there is ongoing discussion about moving Encounter.diagnosis (Procedure|Condition) to Account (at least the billing relevant ones). In that case, the reamining usages of Encounter.diagnosis (as in "reason for admission") could also be collapsed into the reason backbone element!
see https://gforge.hl7.org/gf/project/fhir/tracker/?action=TrackerItemEdit&tracker_item_id=19285

The change could also alleviate some existing confusion about when to use Encounter.reason and when to use Encounter.diagnosis https://gforge.hl7.org/gf/project/fhir/tracker/?action=TrackerItemEdit&tracker_item_id=16148&start=0

The change would also allow for more flexibility in documenting Encounter outcome https://gforge.hl7.org/gf/project/fhir/tracker/?action=TrackerItemEdit&tracker_item_id=17304&start=0

In Germany stating admission- and discharge reasons is required for all Encounters, there are mandatory ValueSets for coding these reasons