feature #28815 YamlEncoder handle yml format (kevin-biig)

This PR was merged into the 4.2-dev branch.

Discussion
----------

YamlEncoder handle yml format

| Q             | A
| ------------- | ---
| Branch?       | ?
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #28768
| License       | MIT

`Symfony\Component\Serializer\Encoder\YamlEncoder` now handle the `yml` format too

```
use Symfony\Component\Serializer\Serializer;
use Symfony\Component\Serializer\Encoder\YamlEncoder;

$serializer = new Serializer([], [new YamlEncoder()]);
$content = file_get_contents(__DIR__ . '/test.yml');
$data = $serializer->decode($content, YamlEncoder::ALTERNATIVE_FORMAT);
```

Let me know if something is wrong for you

Commits
-------

d8640f965b YamlEncoder handle yml extension

src/Symfony/Component/Serializer/CHANGELOG.md

@@ -23,6 +23,7 @@ CHANGELOG
  * added the optional `$objectClassResolver` argument in `AbstractObjectNormalizer`
    and `ObjectNormalizer` constructor
  * added `MetadataAwareNameConverter` to configure the serialized name of properties through metadata
+ * `YamlEncoder` now handle the `.yml` extension too
 
 4.1.0
 -----

src/Symfony/Component/Serializer/Encoder/YamlEncoder.php

@@ -23,6 +23,7 @@ use Symfony\Component\Yaml\Parser;
 class YamlEncoder implements EncoderInterface, DecoderInterface
 {
     const FORMAT = 'yaml';
+    const ALTERNATIVE_FORMAT = 'yml';
 
     private $dumper;
     private $parser;
@@ -54,7 +55,7 @@ class YamlEncoder implements EncoderInterface, DecoderInterface
      */
     public function supportsEncoding($format)
     {
-        return self::FORMAT === $format;
+        return self::FORMAT === $format || self::ALTERNATIVE_FORMAT === $format;
     }
 
     /**
@@ -72,6 +73,6 @@ class YamlEncoder implements EncoderInterface, DecoderInterface
      */
     public function supportsDecoding($format)
     {
-        return self::FORMAT === $format;
+        return self::FORMAT === $format || self::ALTERNATIVE_FORMAT === $format;
     }
 }

src/Symfony/Component/Serializer/Tests/Encoder/YamlEncoderTest.php

@@ -35,6 +35,7 @@ class YamlEncoderTest extends TestCase
         $encoder = new YamlEncoder();
 
         $this->assertTrue($encoder->supportsEncoding('yaml'));
+        $this->assertTrue($encoder->supportsEncoding('yml'));
         $this->assertFalse($encoder->supportsEncoding('json'));
     }
 
@@ -51,6 +52,7 @@ class YamlEncoderTest extends TestCase
         $encoder = new YamlEncoder();
 
         $this->assertTrue($encoder->supportsDecoding('yaml'));
+        $this->assertTrue($encoder->supportsDecoding('yml'));
         $this->assertFalse($encoder->supportsDecoding('json'));
     }