FEATURE: Introduce an utility to add log environment from method name

This utility can be used to easily add the log environment to log
message using the PSR compatible logger.

Example:

```
$logger->debug('Running sub process loop.', LogEnvironment::fromMethodName(__METHOD__));
```

Neos.Flow/Classes/Log/Utility/LogEnvironment.php

@@ -0,0 +1,94 @@
+<?php
+namespace Neos\Flow\Log\Utility;
+
+/*
+ * This file is part of the Neos.Flow package.
+ *
+ * (c) Contributors of the Neos Project - www.neos.io
+ *
+ * This package is Open Source Software. For the full copyright and license
+ * information, please view the LICENSE file which was distributed with this
+ * source code.
+ */
+
+use Neos\Flow\Core\Bootstrap;
+use Neos\Flow\Package\PackageInterface;
+use Neos\Flow\Package\PackageKeyAwareInterface;
+use Neos\Flow\Package\PackageManager;
+use Neos\Flow\Package\PackageManagerInterface;
+use Neos\Utility\Arrays;
+
+abstract class LogEnvironment
+{
+
+    /**
+     * @var array
+     */
+    protected static $packageKeys = null;
+
+    /**
+     * Returns an array containing the log environment variables
+     * under the key FLOW_LOG_ENVIRONMENT to be set as part of the additional data
+     * in an log method call.
+     *
+     * @param string $methodName
+     * @return array
+     */
+    public static function fromMethodName(string $methodName): array
+    {
+        list($className, $functionName) = explode('::', $methodName);
+
+        return [
+            'FLOW_LOG_ENVIRONMENT' => [
+                'packageKey' => self::getPackageKeyFromClassName($className),
+                'className' => $className,
+                'methodName' => $functionName
+            ]
+        ];
+    }
+
+    /**
+     * @param string $className
+     * @return string
+     */
+    protected static function getPackageKeyFromClassName(string $className): string
+    {
+        $packageKeys = self::getPackageKeys();
+        $classPathArray = explode('\\', $className);
+
+        $determinedPackageKey = array_shift($classPathArray);
+        $packageKeyCandidate = $determinedPackageKey;
+
+        foreach ($classPathArray as $classPathSegment) {
+            $packageKeyCandidate = $packageKeyCandidate . '.' . $classPathSegment;
+
+            if (!isset($packageKeys[$packageKeyCandidate])) {
+                continue;
+            }
+
+            $determinedPackageKey = $packageKeyCandidate;
+        }
+
+        return $determinedPackageKey;
+    }
+
+    /**
+     * @return array
+     */
+    protected static function getPackageKeys(): array
+    {
+        if (self::$packageKeys === null) {
+            /** @var PackageManagerInterface $packageManager */
+            $packageManager = Bootstrap::$staticObjectManager->get(PackageManager::class);
+
+            /** @var PackageInterface $package */
+            foreach ($packageManager->getAvailablePackages() as $package) {
+                if ($package instanceof PackageKeyAwareInterface) {
+                    self::$packageKeys[$package->getPackageKey()] = true;
+                }
+            }
+        }
+
+        return self::$packageKeys;
+    }
+}

Neos.Flow/Tests/Functional/Log/Utility/LogEnvironmentTest.php

@@ -0,0 +1,63 @@
+<?php
+namespace Neos\Flow\Tests\Functional\Log\Utility;
+
+/*
+ * This file is part of the Neos.Flow package.
+ *
+ * (c) Contributors of the Neos Project - www.neos.io
+ *
+ * This package is Open Source Software. For the full copyright and license
+ * information, please view the LICENSE file which was distributed with this
+ * source code.
+ */
+
+use Neos\Flow\Log\Utility\LogEnvironment;
+use Neos\Flow\Tests\FunctionalTestCase;
+
+class LogEnvironmentTest extends FunctionalTestCase
+{
+
+    /**
+     * @return array
+     */
+    public function fromMethodNameDataProvider(): array
+    {
+        return [
+            'packageKeyCanBeDetermined' => [
+                'method' => __METHOD__,
+                'expected' => [
+                    'FLOW_LOG_ENVIRONMENT' => [
+                        'packageKey' => 'Neos.Flow',
+                        'className' => 'Neos\Flow\Tests\Functional\Log\Utility\LogEnvironmentTest',
+                        'methodName' => 'fromMethodNameDataProvider'
+                    ]
+                ]
+            ],
+            'unknownPackageKeyReturnsFirstPart' => [
+                'method' => 'Some\Unknown\CLass\Path::methodName',
+                'expected' => [
+                    'FLOW_LOG_ENVIRONMENT' => [
+                        'packageKey' => 'Some',
+                        'className' => 'Some\Unknown\CLass\Path',
+                        'methodName' => 'methodName'
+                    ]
+                ]
+            ]
+        ];
+    }
+
+
+    /**
+     * @test
+     *
+     * @param $method
+     * @param $expected
+     *
+     * @dataProvider fromMethodNameDataProvider
+     */
+    public function fromMethodName($method, $expected)
+    {
+        $actual = LogEnvironment::fromMethodName($method);
+        $this->assertEquals($expected, $actual);
+    }
+}