refactor: improve null safety in lookup resources

- Make country, networkCode, countryCode properties nullable in Carrier
- Make countryCode property nullable in LookupHlr
- Better handle API responses with missing data

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: cl77

src/Resource/Lookup/Carrier.php

@@ -3,27 +3,27 @@
 namespace Seven\Api\Resource\Lookup;
 
 class Carrier {
-    protected string $country;
+    protected ?string $country;
     protected ?string $name;
-    protected string $networkCode;
+    protected ?string $networkCode;
     protected ?string $networkType;
 
     public function __construct(object $data) {
-        $this->country = $data->country;
+        $this->country = $data->country ?: null;
         $this->name = $data->name;
-        $this->networkCode = $data->network_code;
+        $this->networkCode = $data->network_code ?: null;
         $this->networkType = $data->network_type;
     }
 
-    public function getCountry(): string {
+    public function getCountry(): ?string {
         return $this->country;
     }
 
     public function getName(): ?string {
         return $this->name;
     }
 
-    public function getNetworkCode(): string {
+    public function getNetworkCode(): ?string {
         return $this->networkCode;
     }
 

src/Resource/Lookup/LookupHlr.php

@@ -3,7 +3,7 @@
 namespace Seven\Api\Resource\Lookup;
 
 class LookupHlr {
-    protected string $countryCode;
+    protected ?string $countryCode;
     protected ?string $countryName;
     protected string|false $countryPrefix;
     protected Carrier $currentCarrier;
@@ -23,7 +23,7 @@ class LookupHlr {
     protected string $validNumber;
 
     public function __construct(object $data) {
-        $this->countryCode = $data->country_code;
+        $this->countryCode = $data->country_code ?: null;
         $this->countryName = $data->country_name;
         $this->countryPrefix = $data->country_prefix;
         $this->currentCarrier = new Carrier($data->current_carrier);
@@ -43,7 +43,7 @@ public function __construct(object $data) {
         $this->validNumber = $data->valid_number;
     }
 
-    public function getCountryCode(): string {
+    public function getCountryCode(): ?string {
         return $this->countryCode;
     }