Implement PHP CS Fixer and a coding standard to follow (#471)

* Create PHP CS Fixer config and add to CI workflow

* Run php cs fixer on project

* Add newline at end of file

* Update to use PHP CS Fixer v3

* Run v3 config on project

* Run seperate config in CI

database/factories/PaymentFactory.php

@@ -28,7 +28,7 @@ class PaymentFactory extends Factory
             'payment_date' => $this->faker->date('Y-m-d', 'now'),
             'notes' => $this->faker->text(80),
             'amount' => $this->faker->randomDigitNotNull,
-            'payment_number' => 'PAY-' . Payment::getNextPaymentNumber('PAY'),
+            'payment_number' => 'PAY-'.Payment::getNextPaymentNumber('PAY'),
         ];
     }
 }