Default smoking to "unknown" (#5501)

**Story card:**
[sc-14262](https://app.shortcut.com/simpledotorg/story/14262/update-smoking-to-default-to-unknown)

## Because

`smoking` should act like other questions in `medical_histories`

## This addresses

Ensuring `smoking` presents as "unknown" to clients when it's not set in
the server

## Test instructions

- introduced a new test for the scenario

Author: igbanam

app/schema/api/v3/models.rb

@@ -307,6 +307,7 @@ def medical_history
          diabetes: {type: :string, enum: MedicalHistory::MEDICAL_HISTORY_ANSWERS.keys},
          hypertension: {type: :string, enum: MedicalHistory::MEDICAL_HISTORY_ANSWERS.keys},
          diagnosed_with_hypertension: {type: :string, enum: MedicalHistory::MEDICAL_HISTORY_ANSWERS.keys},
+         smoking: {type: :string, enum: MedicalHistory::MEDICAL_HISTORY_ANSWERS.keys},
          deleted_at: {"$ref" => "#/definitions/nullable_timestamp"},
          created_at: {"$ref" => "#/definitions/timestamp"},
          updated_at: {"$ref" => "#/definitions/timestamp"}

app/transformers/api/v3/medical_history_transformer.rb

@@ -5,6 +5,7 @@ def to_response(medical_history)
         .to_response(medical_history)
         .except("user_id")
         .except(*MedicalHistory::MEDICAL_HISTORY_QUESTIONS.map { |question| "#{question}_boolean" })
+        .tap { |params| params["smoking"] ||= "unknown" }
     end
 
     def from_request(medical_history_payload)

spec/controllers/api/v3/medical_histories_controller_spec.rb

@@ -67,6 +67,18 @@ def create_record_list(n, options = {})
         expect(response_2_records.map(&:patient).to_set).to eq Set[patient_in_request_facility, patient_in_same_group]
       end
     end
+
+    context "non-nullable smoking" do
+      let(:patient_in_request_facility) { build(:patient, registration_facility: request_facility) }
+      it "defaults smoking to 'unknown'" do
+        create(:medical_history, :without_smoking, patient: patient_in_request_facility)
+        set_authentication_headers
+        get :sync_to_user
+        response_body = JSON(response.body)
+        expect(response_body["medical_histories"][0]["smoking"]).not_to be nil
+        expect(response_body["medical_histories"][0]["smoking"]).to eq "unknown"
+      end
+    end
   end
 
   describe "#sync_from_user" do

spec/factories/medical_histories.rb

@@ -64,6 +64,10 @@
       hypertension { "yes" }
       chronic_kidney_disease { "yes" }
     end
+
+    trait :without_smoking do
+      smoking { nil }
+    end
   end
 end