feat: derive outcode centroids from postcodes during import

tests/Feature/Console/ImportPostcodesTest.php

@@ -1,5 +1,6 @@
 <?php
 
+use App\Models\Outcode;
 use App\Models\Postcode;
 use Illuminate\Foundation\Testing\RefreshDatabase;
 
@@ -61,3 +62,23 @@ CSV;
     expect(Postcode::count())->toBe(1)
         ->and(Postcode::find('BT11AA'))->toBeNull();
 });
+
+it('derives outcode centroids as the average of member postcodes', function (): void {
+    $csv = <<<'CSV'
+pcd,pcds,doterm,lat,long
+"PE71AA","PE7 1AA","",52.500000,-0.200000
+"PE71AB","PE7 1AB","",52.600000,-0.220000
+"M11AD","M1 1AD","",53.480957,-2.237428
+CSV;
+
+    $path = writeOnspdFixture($csv);
+
+    $this->artisan('postcodes:import', ['--file' => $path])->assertSuccessful();
+
+    $pe7 = Outcode::find('PE7');
+
+    expect($pe7)->not->toBeNull()
+        ->and(round((float) $pe7->lat, 6))->toBe(52.550000)
+        ->and(round((float) $pe7->lng, 6))->toBe(-0.210000)
+        ->and(Outcode::find('M1'))->not->toBeNull();
+});