Use facility additional value and not channel to be compat with existing Monolog 3 code

src/Monolog/Formatter/GelfMessageFormatter.php

@@ -135,7 +135,7 @@ class GelfMessageFormatter extends NormalizerFormatter
                 unset($extra['file']);
             }
         } else {
-            $message->setAdditional('channel', $record['channel']);
+            $message->setAdditional('facility', $record['channel']);
         }
 
         foreach ($extra as $key => $val) {

tests/Monolog/Formatter/GelfMessageFormatterTest.php

@@ -50,7 +50,7 @@ class GelfMessageFormatterTest extends TestCase
             $this->assertEquals(null, $message->getLine());
             $this->assertEquals(null, $message->getFile());
         } else {
-            $this->assertEquals('meh', $message->getAdditional('channel'));
+            $this->assertEquals('meh', $message->getAdditional('facility'));
         }
         $this->assertEquals($this->isLegacy() ? 3 : 'error', $message->getLevel());
         $this->assertNotEmpty($message->getHost());
@@ -172,7 +172,7 @@ class GelfMessageFormatterTest extends TestCase
             $this->assertEquals("/some/file/in/dir.php", $message->getFile());
             $this->assertEquals("56", $message->getLine());
         } else {
-            $this->assertEquals(['channel' => 'meh', 'ctxt_exception' => '{"class":"\\\\Exception","file":"/some/file/in/dir.php:56","trace":["/some/file/1.php:23","/some/file/2.php:3"]}'], $message->getAllAdditionals());
+            $this->assertEquals(['facility' => 'meh', 'ctxt_exception' => '{"class":"\\\\Exception","file":"/some/file/in/dir.php:56","trace":["/some/file/1.php:23","/some/file/2.php:3"]}'], $message->getAllAdditionals());
         }
     }
 

tests/Monolog/Handler/GelfHandlerTest.php

@@ -62,7 +62,7 @@ class GelfHandlerTest extends TestCase
         if (self::isGelfVersion1()) {
             $expectedMessage->setFacility("test");
         } else {
-            $expectedMessage->setAdditional('channel', "test");
+            $expectedMessage->setAdditional('facility', "test");
         }
 
         $messagePublisher = $this->getMessagePublisher();
@@ -88,7 +88,7 @@ class GelfHandlerTest extends TestCase
         if (self::isGelfVersion1()) {
             $expectedMessage->setFacility("test");
         } else {
-            $expectedMessage->setAdditional('channel', "test");
+            $expectedMessage->setAdditional('facility', "test");
         }
 
         $messagePublisher = $this->getMessagePublisher();
@@ -120,7 +120,7 @@ class GelfHandlerTest extends TestCase
         if (self::isGelfVersion1()) {
             $expectedMessage->setFacility("test");
         } else {
-            $expectedMessage->setAdditional('channel', "test");
+            $expectedMessage->setAdditional('facility', "test");
         }
 
         $messagePublisher = $this->getMessagePublisher();