How can if fix this Laravel one to many with a custom foreign key behavior

I’m new to laravel and trying to make two tables with a one (customer) to many(table) relation and a custom Foreign Key tables.customer(I can not change this)

The connection is over customers.id on tables.customer.

After Running php artisan migrate:fresh --seed everything is created as expected. But tables.customer is always 0.
I don’t get any errors. And both tables are created correctly.
What do I miss?

Here are my settings:

Models:

Customers.php

namespace AppModels;

use IlluminateDatabaseEloquentFactoriesHasFactory;
use IlluminateDatabaseEloquentModel;

class Customers extends Model {
  use HasFactory;

  public function tables() {
    return $this->hasMany(Tables::class, 'customer');
  }

  public $timestamps = false;
}

Tables.php

namespace AppModels;

use IlluminateDatabaseEloquentFactoriesHasFactory;
use IlluminateDatabaseEloquentModel;

class Tables extends Model {
  use HasFactory;

  public function customers() {
    return $this->belongsTo(Customers::class, 'customer');
  }

  public $timestamps = false;
}

Migration:

customers

use IlluminateDatabaseMigrationsMigration;
use IlluminateDatabaseSchemaBlueprint;
use IlluminateSupportFacadesSchema;

return new class extends Migration {
  /**
   * Run the migrations.
   *
   * @return void
   */
  public function up() {
    Schema::create('customers', function (Blueprint $table) {
      $table->string('id', 6)->primary();
      $table
        ->string('img', 23)
        ->nullable()
        ->default(null);
      $table->tinyText('name');
      $table->tinyInteger('active')->default(1);
      $table->bigInteger('created'); // unix timestamp when created
      $table
        ->bigInteger('status')
        ->nullable()
        ->default(null); // null not deleted / unix timestamp when deleted
    });
  }

  /**
   * Reverse the migrations.
   *
   * @return void
   */
  public function down() {
    Schema::dropIfExists('customers');
  }
};

tables

use IlluminateDatabaseMigrationsMigration;
use IlluminateDatabaseSchemaBlueprint;
use IlluminateSupportFacadesSchema;

return new class extends Migration {
  /**
   * Run the migrations.
   *
   * @return void
   */
  public function up() {
    Schema::create('tables', function (Blueprint $table) {
      $table->string('id', 8)->primary();
      $table->tinyText('number');
      $table->string('customer', 6); // TODO: repalce with uuid
      $table->bigInteger('created'); // unix timestamp when created
      $table
        ->bigInteger('status')
        ->nullable()
        ->default(null); // null not deleted / unix timestamp when deleted
    });
  }

  /**
   * Reverse the migrations.
   *
   * @return void
   */
  public function down() {
    Schema::dropIfExists('tables');
  }
};

Factories:

CustomersFactory.php

namespace DatabaseFactories;

use IlluminateDatabaseEloquentFactoriesFactory;

/**
 * @extends IlluminateDatabaseEloquentFactoriesFactory<AppModelsCustomers>
 */
class CustomersFactory extends Factory {
  /**
   * Define the model's default state.
   *
   * @return array<string, mixed>
   */
  public function definition() {
    return [
      'id' => $this->faker->unique()->regexify('[A-Za-z0-9]{6}'),
      'name' => $this->faker->company(),
      'active' => $this->faker->boolean(),
      'created' => $this->faker->unixTime(),
      'status' => $this->faker->boolean() ? null : $this->faker->unixTime(),
    ];
  }
}

TablesFactory.php

namespace DatabaseFactories;

use AppModelsCustomers;
use IlluminateDatabaseEloquentFactoriesFactory;

/**
 * @extends IlluminateDatabaseEloquentFactoriesFactory<AppModelsTables>
 */
class TablesFactory extends Factory {
  /**
   * Define the model's default state.
   *
   * @return array<string, mixed>
   */
  public function definition() {
    return [
      'id' => $this->faker->unique()->regexify('[A-Za-z0-9]{8}'),
      'number' => $this->faker->unique()->numberBetween(1, 1000),
      'customer' => Customers::factory()->create()->id,
      'created' => $this->faker->unixTime(),
      'status' => $this->faker->boolean() ? null : $this->faker->unixTime(),
    ];
  }
}

Seeders:

customersSeeder.php

namespace DatabaseSeeders;

use AppModelsCustomers;
use IlluminateDatabaseConsoleSeedsWithoutModelEvents;
use IlluminateDatabaseSeeder;

class CustomersSeeder extends Seeder {
  /**
   * Run the database seeds.
   *
   * @return void
   */
  public function run() {
    Customers::factory()
      ->count(10)
      ->hasTables(20)
      ->create();
  }
}

TablesSeeder.php

namespace DatabaseSeeders;

use AppModelsTables;
use IlluminateDatabaseConsoleSeedsWithoutModelEvents;
use IlluminateDatabaseSeeder;

class TablesSeeder extends Seeder {
  /**
   * Run the database seeds.
   *
   * @return void
   */
  public function run() {
    //
  }
}

DatabaseSeeder.php

namespace DatabaseSeeders;

// use IlluminateDatabaseConsoleSeedsWithoutModelEvents;
use IlluminateDatabaseSeeder;

class DatabaseSeeder extends Seeder {
  /**
   * Seed the application's database.
   *
   * @return void
   */
  public function run() {
    $this->call([CustomersSeeder::class]);
  }
}