Add routes and objects for managing collected order invoices

Introduced GET and POST endpoints for collected order invoices, enabling listing and creation functionalities for authorized users. Added a new database object to handle invoice-related operations and validations. Included utility functions to enforce parameter requirements and data integrity.

services/nginx/app/traits/route_t.php

@@ -39,11 +39,24 @@ trait route_t
         return true;
     }
 
+    public function requireMinValue(int $value, int $min): void
+    {
+        global $response;
+        if ($value < $min) {
+            $response->error('Parameter must be at least ' . $min, 400);
+        }
+    }
+
     public function type_int(): string
     {
         return 'integer';
     }
 
+    public function type_string(): string
+    {
+        return 'string';
+    }
+
     public function requireParameters(array $parameters): void
     {
         global $response;