feat(ffe): Add OpenFeature provider implementation

Add DDTrace\OpenFeature\DataDogProvider that implements the
OpenFeature PHP SDK's AbstractProvider interface, wrapping the
internal FFE evaluation engine.

Author: leoromanovsky

src/DDTrace/OpenFeature/DataDogProvider.php

@@ -0,0 +1,126 @@
+<?php
+
+namespace DDTrace\OpenFeature;
+
+use DDTrace\FeatureFlags\Provider;
+use OpenFeature\implementation\provider\AbstractProvider;
+use OpenFeature\implementation\provider\ResolutionDetailsBuilder;
+use OpenFeature\interfaces\flags\EvaluationContext;
+use OpenFeature\interfaces\provider\Metadata;
+use OpenFeature\interfaces\provider\ResolutionDetails as ResolutionDetailsInterface;
+
+/**
+ * Datadog OpenFeature Provider.
+ *
+ * Implements the OpenFeature Provider interface for Datadog's
+ * Feature Flags and Experimentation (FFE) product.
+ *
+ * Usage:
+ *   use OpenFeature\API;
+ *   use DDTrace\OpenFeature\DataDogProvider;
+ *
+ *   API::setProvider(new DataDogProvider());
+ *   $client = API::getClient();
+ *   $value = $client->getBooleanValue('my-flag', false, $context);
+ *
+ * Requires: composer require open-feature/sdk
+ */
+class DataDogProvider extends AbstractProvider
+{
+    /** @var Provider */
+    private $ffeProvider;
+
+    public function __construct()
+    {
+        $this->ffeProvider = Provider::getInstance();
+        $this->ffeProvider->start();
+    }
+
+    public function getMetadata(): Metadata
+    {
+        return new class implements Metadata {
+            public function getName(): string
+            {
+                return 'Datadog';
+            }
+        };
+    }
+
+    public function resolveBooleanValue(
+        string $flagKey,
+        bool $defaultValue,
+        ?EvaluationContext $context = null
+    ): ResolutionDetailsInterface {
+        return $this->resolve($flagKey, 'BOOLEAN', $defaultValue, $context);
+    }
+
+    public function resolveStringValue(
+        string $flagKey,
+        string $defaultValue,
+        ?EvaluationContext $context = null
+    ): ResolutionDetailsInterface {
+        return $this->resolve($flagKey, 'STRING', $defaultValue, $context);
+    }
+
+    public function resolveIntegerValue(
+        string $flagKey,
+        int $defaultValue,
+        ?EvaluationContext $context = null
+    ): ResolutionDetailsInterface {
+        return $this->resolve($flagKey, 'INTEGER', $defaultValue, $context);
+    }
+
+    public function resolveFloatValue(
+        string $flagKey,
+        float $defaultValue,
+        ?EvaluationContext $context = null
+    ): ResolutionDetailsInterface {
+        return $this->resolve($flagKey, 'NUMERIC', $defaultValue, $context);
+    }
+
+    public function resolveObjectValue(
+        string $flagKey,
+        array $defaultValue,
+        ?EvaluationContext $context = null
+    ): ResolutionDetailsInterface {
+        return $this->resolve($flagKey, 'JSON', $defaultValue, $context);
+    }
+
+    /**
+     * @param mixed $defaultValue
+     */
+    private function resolve(
+        string $flagKey,
+        string $variationType,
+        $defaultValue,
+        ?EvaluationContext $context = null
+    ): ResolutionDetailsInterface {
+        $targetingKey = '';
+        $attributes = [];
+
+        if ($context !== null) {
+            $targetingKey = $context->getTargetingKey() ?? '';
+            $attrs = $context->getAttributes();
+            if ($attrs !== null) {
+                $attributes = $attrs->toArray();
+            }
+        }
+
+        $result = $this->ffeProvider->evaluate(
+            $flagKey,
+            $variationType,
+            $defaultValue,
+            $targetingKey,
+            $attributes
+        );
+
+        $builder = new ResolutionDetailsBuilder();
+        $builder->withValue($result['value']);
+
+        if (isset($result['reason'])) {
+            $builder->withReason($result['reason']);
+        }
+
+        return $builder->build();
+    }
+}