feat: add backward compatibility for CompletionProvider providerClass parameter

Maintains support for existing `providerClass` parameter while encouraging
migration to the new `provider` parameter for consistency.

Author: CodeWithKyrian

src/Attributes/CompletionProvider.php

@@ -11,9 +11,11 @@
 class CompletionProvider
 {
     /**
+     * @param class-string<CompletionProviderInterface>|null $providerClass 
      * @param class-string<CompletionProviderInterface>|CompletionProviderInterface|null $provider If a class-string, it will be resolved from the container at the point of use.
      */
     public function __construct(
+        public ?string $providerClass = null,
         public string|CompletionProviderInterface|null $provider = null,
         public ?array $values = null,
         public ?string $enum = null,

src/ServerBuilder.php

@@ -511,6 +511,8 @@ private function getCompletionProviders(\ReflectionMethod|\ReflectionFunction $r
 
                 if ($attributeInstance->provider) {
                     $completionProviders[$param->getName()] = $attributeInstance->provider;
+                } elseif ($attributeInstance->providerClass) {
+                    $completionProviders[$param->getName()] = $attributeInstance->providerClass;
                 } elseif ($attributeInstance->values) {
                     $completionProviders[$param->getName()] = new ListCompletionProvider($attributeInstance->values);
                 } elseif ($attributeInstance->enum) {

src/Utils/Discoverer.php

@@ -268,6 +268,8 @@ private function getCompletionProviders(\ReflectionMethod $reflectionMethod): ar
 
                 if ($attributeInstance->provider) {
                     $completionProviders[$param->getName()] = $attributeInstance->provider;
+                } elseif ($attributeInstance->providerClass) {
+                    $completionProviders[$param->getName()] = $attributeInstance->provider;
                 } elseif ($attributeInstance->values) {
                     $completionProviders[$param->getName()] = new ListCompletionProvider($attributeInstance->values);
                 } elseif ($attributeInstance->enum) {