feat: standardize invoice number field, refine invoice creation logic, and update module foreign key constraints

database/migrations/2024_02_03_095630_module_vmware.php

@@ -18,10 +18,10 @@ return new class extends Migration
             $table->string('name')->nullable();
 
             $table->foreignId('module_ip_address')
-                ->constrained('module_ip_address');
+                ->constrained('module_ip_address')->nullable();
 
             $table->foreignId('vcenter_id')
-                ->constrained('module_vcenter');
+                ->constrained('module_vcenter')->nullable();
 
             $table->integer('port')->nullable();
             $table->integer('order_id')->nullable();