Added customer_nr to database and invoice templates.

Used standard DATEV format(10000 – 69999)

Fixes #31

database/factories/CustomerFactory.php

@@ -3,6 +3,7 @@
 namespace Database\Factories;
 use App\Models\PaymentTerms;
 use Illuminate\Database\Eloquent\Factories\Factory;
+use App\Http\Controllers\CustomerController;
 
 class CustomerFactory extends Factory
 {
@@ -13,6 +14,7 @@ public function definition()
         return [
             'type' => $this->faker->randomElement(['private', 'business']),
             'company_name' => $this->faker->company(),
+            'customer_nr' => CustomerController::generateCustomerNumber(),
             'vat_id' => $this->faker->numerify('DE##########'),
             'tax_id' => $this->faker->numerify('DE##########'),
             'global_id' => $this->faker->numerify('############'),

database/migrations/2025_09_17_000000_create_customers_table.php

@@ -11,6 +11,7 @@ public function up()
             $table->id();
             $table->enum('type', ['private', 'business']);
             $table->string('company_name', 100)->nullable();
+            $table->integer('customer_nr', false, true)->nullable();
             $table->string('vat_id', 50)->nullable();
             $table->string('tax_id', 50)->nullable();
             $table->string('global_id', 50)->nullable();