Add Bird API integration with voice call and flash call support

- Implement Bird API client (`bird.php`) for handling HTTP requests to Bird services.
- Add routes for voice and flash call management (`birdVoiceFlashCallsRoute.php`, `birdNumbersRoute.php`).
- Introduce test cases for voice calls, flash calls, and numbers (`VoiceCallsApiTest.php`, `NumbersAndFlashCallsApiTest.php`).
- Include configuration management classes and APIs for enabling the Bird module and managing API keys (`bird_c.php`).
- Provide OpenAPI specifications for flash call endpoints (`bird-flash-calls.md`).

services/nginx/app/modules/bird/config/bird_enabled_c.php

@@ -0,0 +1,31 @@
+<?php
+
+namespace bird\config;
+
+require_once WD . '/traits/module_config_variable_t.php';
+
+use Exception;
+use traits\module_config_variable;
+
+class bird_enabled_c
+{
+    use module_config_variable;
+
+    /**
+     * @throws Exception
+     */
+    public function __construct()
+    {
+        self::setupConfigVariable(
+            'bird',
+            'enabled',
+            'bool',
+            true,
+            null,
+            'Whether the Bird module is enabled or not',
+            'true',
+            false,
+            'false'
+        );
+    }
+}