Refactor startup modification and environment variable services

Better setup, more flexibility, more tests.

database/factories/ModelFactory.php

@@ -29,6 +29,9 @@ $factory->define(Pterodactyl\Models\Server::class, function (Faker\Generator $fa
         'io' => 500,
         'cpu' => 0,
         'oom_disabled' => 0,
+        'allocation_id' => $faker->randomNumber(),
+        'nest_id' => $faker->randomNumber(),
+        'egg_id' => $faker->randomNumber(),
         'pack_id' => null,
         'installed' => 1,
         'created_at' => \Carbon\Carbon::now(),