Resolve the issue that external does not serialize by atproto/bsky specs

- Add Client dependency to External constructor for future use
- Restructure jsonSerialize output to match required format
- Wrap external data in 'external' property according to spec
- Update unit tests to reflect new structure
- Fix array formatting and indentation in tests

This commit addresses an issue where external embeds weren't being
structured according to AT Protocol specifications, which requires
external data to be nested under an 'external' property.

src/Lexicons/App/Bsky/Embed/External.php

@@ -2,6 +2,7 @@
 
 namespace Atproto\Lexicons\App\Bsky\Embed;
 
+use Atproto\Client;
 use Atproto\Contracts\Lexicons\App\Bsky\Embed\EmbedInterface;
 use Atproto\Contracts\Lexicons\App\Bsky\Embed\MediaContract;
 use Atproto\DataModel\Blob\Blob;
@@ -17,7 +18,7 @@ class External implements EmbedInterface, MediaContract
     private string $description;
     private ?Blob $blob = null;
 
-    public function __construct(string $uri, string $title, string $description)
+    public function __construct(Client $bsky, string $uri, string $title, string $description)
     {
         $this->uri($uri)
             ->title($title)
@@ -94,12 +95,14 @@ public function thumb(Blob $blob = null)
 
     public function jsonSerialize(): array
     {
-        return array_filter([
+        return [
             '$type' => $this->nsid(),
-            'uri' => $this->uri,
-            'title' => $this->title,
-            'description' => $this->description,
-            'blob' => ($b = $this->blob) ? $b : null,
-        ]);
+            'external' => array_filter([
+                'uri' => $this->uri,
+                'title' => $this->title,
+                'description' => $this->description,
+                'blob' => ($b = $this->blob) ? $b : null,
+            ])
+        ];
     }
 }

tests/Unit/Lexicons/App/Bsky/Embed/ExternalTest.php

@@ -2,6 +2,7 @@
 
 namespace Tests\Unit\Lexicons\App\Bsky\Embed;
 
+use Atproto\Client;
 use Atproto\DataModel\Blob\Blob;
 use Atproto\Exceptions\InvalidArgumentException;
 use Atproto\Lexicons\App\Bsky\Embed\External;
@@ -17,7 +18,7 @@ class ExternalTest extends TestCase
 
     public function setUp(): void
     {
-        $this->external = new External('https://shahmal1yev.dev', 'foo', 'bar');
+        $this->external = new External($this->createMock(Client::class), 'https://shahmal1yev.dev', 'foo', 'bar');
 
         $this->blob = $this->getMockBuilder(Blob::class)
             ->disableOriginalConstructor()
@@ -107,9 +108,11 @@ public function testJsonSerializeWithoutSetBlob(): void
     {
         $expected = [
             '$type' => 'app.bsky.embed.external',
-            'uri' => 'https://shahmal1yev.dev',
-            'title' => 'foo',
-            'description' => 'bar',
+            'external' => [
+                'uri' => 'https://shahmal1yev.dev',
+                'title' => 'foo',
+                'description' => 'bar',
+            ]
         ];
 
         $this->assertSame($expected, json_decode($this->external, true));
@@ -124,10 +127,12 @@ public function testJsonSerializeWithSetBlob(): void
 
         $expected = [
             '$type' => 'app.bsky.embed.external',
-            'uri' => 'https://shahmal1yev.dev',
-            'title' => 'foo',
-            'description' => 'bar',
-            'blob' => $this->blob->jsonSerialize(),
+            'external' => [
+                'uri' => 'https://shahmal1yev.dev',
+                'title' => 'foo',
+                'description' => 'bar',
+                'blob' => $this->blob->jsonSerialize()
+            ],
         ];
 
         $this->assertSame($expected, json_decode($this->external, true));