Add SDK TracerProviderInterface to expose ::shutdown() and ::forceFlush() (#756)

Author: Nevay

src/SDK/Trace/TracerProvider.php

@@ -18,7 +18,7 @@
 use function spl_object_id;
 use WeakReference;
 
-final class TracerProvider implements API\TracerProviderInterface
+final class TracerProvider implements TracerProviderInterface
 {
     /** @var array<int, WeakReference<self>>|null */
     private static ?array $tracerProviders = null;
@@ -58,7 +58,7 @@ public function __construct(
         self::registerShutdownFunction($this);
     }
 
-    public function forceFlush(): ?bool
+    public function forceFlush(): bool
     {
         return $this->tracerSharedState->getSpanProcessor()->forceFlush();
     }

src/SDK/Trace/TracerProviderFactory.php

@@ -4,7 +4,6 @@
 
 namespace OpenTelemetry\SDK\Trace;
 
-use OpenTelemetry\API\Trace as API;
 use OpenTelemetry\SDK\Behavior\LogsMessagesTrait;
 
 final class TracerProviderFactory
@@ -26,7 +25,7 @@ public function __construct(
         $this->spanProcessorFactory = $spanProcessorFactory ?: new SpanProcessorFactory();
     }
 
-    public function create(): API\TracerProviderInterface
+    public function create(): TracerProviderInterface
     {
         try {
             $exporter = $this->exporterFactory->fromEnvironment();

src/SDK/Trace/TracerProviderInterface.php

@@ -0,0 +1,14 @@
+<?php
+
+declare(strict_types=1);
+
+namespace OpenTelemetry\SDK\Trace;
+
+use OpenTelemetry\API\Trace as API;
+
+interface TracerProviderInterface extends API\TracerProviderInterface
+{
+    public function forceFlush(): bool;
+
+    public function shutdown(): bool;
+}