feat(api): expose n_Apartment on GET /data/:code

docs/openapi/openapi.yaml

@@ -420,6 +420,9 @@ components:
         Year2_Building are the earliest/latest construction year of this
         variant's period band (0 and 9999 are the same open-ended sentinels
         used by /api/v1/periods).
+        BasicParameters.BuildingAppearance.n_Apartment is the number of
+        dwellings in the archetype building: 1 for SFH and TH, the block's
+        dwelling count for MFH and AB, 0 where TABULA gives no count.
       properties:
         BasicParameters:
           type: object

internal/db/repository/repository_integration_test.go

@@ -125,6 +125,16 @@ func seedFixtures(ctx context.Context, pool *pgxpool.Pool) error {
 			('AT.N.MFH.02.Gen',  'AT.02', 1919, 1944),
 			('AT.N.TH.01.Gen',   'AT.01', 0,    1918),
 			('AT.N.TH.05.Gen',   'AT.05', 2000, 9999)`,
+		// netherlands carries the dwelling count. REAL matches the type the
+		// workbook loader gives the column in every country table.
+		`CREATE TABLE tabula.netherlands (
+			id SERIAL PRIMARY KEY,
+			"Code_BuildingVariant" VARCHAR,
+			"n_Apartment" REAL
+		)`,
+		`INSERT INTO tabula.netherlands ("Code_BuildingVariant", "n_Apartment") VALUES
+			('NL.N.AB.03.Gen.ReEx.001.001',  15),
+			('NL.N.SFH.01.Gen.ReEx.001.001', 1)`,
 	}
 	for _, stmt := range statements {
 		if _, err := pool.Exec(ctx, stmt); err != nil {
@@ -257,6 +267,25 @@ func TestTabulaRepository_GetVariant_success(t *testing.T) {
 	}
 }
 
+func TestTabulaRepository_GetVariant_nApartment(t *testing.T) {
+	r := repository.NewTabulaRepository(testPool, "tabula")
+	for _, tc := range []struct {
+		code string
+		want int
+	}{
+		{"NL.N.AB.03.Gen.ReEx.001.001", 15},
+		{"NL.N.SFH.01.Gen.ReEx.001.001", 1},
+	} {
+		params, _, _, err := r.GetVariant(context.Background(), "netherlands", tc.code)
+		if err != nil {
+			t.Fatalf("%s: unexpected error: %v", tc.code, err)
+		}
+		if got := params.BasicParameters.BuildingAppearance.N_Apartment; got != tc.want {
+			t.Errorf("%s: N_Apartment = %d, want %d", tc.code, got, tc.want)
+		}
+	}
+}
+
 func TestTabulaRepository_GetVariant_notFound(t *testing.T) {
 	r := repository.NewTabulaRepository(testPool, "tabula")
 	_, _, _, err := r.GetVariant(context.Background(), "germany", "DE.N.SFH.99.Gen")

internal/db/repository/struct_mapper_test.go

@@ -30,6 +30,7 @@ func TestPopulateStructFromMap_setsFieldsByJSONTag(t *testing.T) {
 		"n_air_infiltration":   float64(0.5),
 		"Year1_Building":       int32(0),
 		"Year2_Building":       int32(1918),
+		"n_Apartment":          float32(15),
 	}
 
 	populateStructFromMap(data, dataMap)
@@ -58,6 +59,9 @@ func TestPopulateStructFromMap_setsFieldsByJSONTag(t *testing.T) {
 	if data.BasicParameters.BuildingAppearance.Year2_Building != 1918 {
 		t.Errorf("Year2_Building = %d, want 1918", data.BasicParameters.BuildingAppearance.Year2_Building)
 	}
+	if data.BasicParameters.BuildingAppearance.N_Apartment != 15 {
+		t.Errorf("N_Apartment = %d, want 15", data.BasicParameters.BuildingAppearance.N_Apartment)
+	}
 }
 
 func TestPopulateStructFromMap_missingAndNilKeysAreSkipped(t *testing.T) {

internal/models/tabula.go

@@ -55,6 +55,7 @@ type BuildingThematic struct {
 	Code_ComplexFootprint   string  `json:"Code_ComplexFootprint"`   // Complexity of building footprint (e.g. "Simple", "Standard", "Complex")
 	Code_ComplexRoof        string  `json:"Code_ComplexRoof"`        // Complexity of roof shape (e.g. "Simple", "Standard", "Complex")
 	N_Storey                int     `json:"n_Storey"`                // Number of storeys (used for calculating conditioned volume if not provided in dataset)
+	N_Apartment             int     `json:"n_Apartment"`             // Number of dwellings in the archetype building (1 for SFH and TH, 0 where TABULA gives no count)
 	H_room                  float64 `json:"h_room"`                  // Room height in meters (used for calculating conditioned volume if not provided in dataset)
 	Code_AtticCond          string  `json:"Code_AtticCond"`          // Attic condition code
 	Code_CellarCond         string  `json:"Code_CellarCond"`         // Cellar condition code