Include egg variables in the output from the API

app/Services/Servers/StartupCommandService.php

@@ -0,0 +1,27 @@
+<?php
+
+namespace Pterodactyl\Services\Servers;
+
+use Pterodactyl\Models\Server;
+
+class StartupCommandService
+{
+    /**
+     * Generates a startup command for a given server instance.
+     *
+     * @param \Pterodactyl\Models\Server $server
+     * @return string
+     */
+    public function handle(Server $server): string
+    {
+        $find = ['{{SERVER_MEMORY}}', '{{SERVER_IP}}', '{{SERVER_PORT}}'];
+        $replace = [$server->memory, $server->allocation->ip, $server->allocation->port];
+
+        foreach ($server->variables as $variable) {
+            $find[] = '{{' . $variable->env_variable . '}}';
+            $replace[] = $variable->user_viewable ? ($variable->server_value ?? $variable->default_value) : '[hidden]';
+        }
+
+        return str_replace($find, $replace, $server->startup);
+    }
+}