MM-60351 Use oEmbed for YouTube links (#28312)

* Split up handling of permalinks and other links in getLinkMetadata

* MM-60351 Use oEmbed for YouTube links

* Explicitly request json from the oEmbed provider

* Fix linter

* Fix type of CacheAge field

* Address feedback

server/channels/app/oembed/endpoint_test.go

@@ -0,0 +1,63 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package oembed
+
+import (
+	"slices"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestFindEndpointForURL(t *testing.T) {
+	youtubeProvider := providers[slices.IndexFunc(providers, func(provider *ProviderEndpoint) bool {
+		return provider.URL == "https://www.youtube.com/oembed"
+	})]
+
+	for _, testCase := range []struct {
+		Name     string
+		Input    string
+		Expected *ProviderEndpoint
+	}{
+		{
+			Name:     "random URL",
+			Input:    "https://example.com/some/random.url",
+			Expected: nil,
+		},
+		{
+			Name:     "YouTube home page",
+			Input:    "https://www.youtube.com",
+			Expected: nil,
+		},
+		{
+			Name:     "YouTube video",
+			Input:    "https://www.youtube.com/watch?v=szfZfQFUSnU",
+			Expected: youtubeProvider,
+		},
+		{
+			Name:     "YouTube video with short link and tracking information",
+			Input:    "https://youtu.be/Qq3zukqBFqQ?si=iK_TPT20H30mH90G",
+			Expected: youtubeProvider,
+		},
+		{
+			Name:     "YouTube video with playlist",
+			Input:    "https://www.youtube.com/watch?v=Qq3zukqBFqQ&list=PL-jqvaPsjQpMqnRgFEw_3fuGQbcVDTpaM",
+			Expected: youtubeProvider,
+		},
+		{
+			Name:     "YouTube playlist",
+			Input:    "https://www.youtube.com/playlist?list=PL-jqvaPsjQpMqnRgFEw_3fuGQbcVDTpaM",
+			Expected: youtubeProvider,
+		},
+		{
+			Name:     "YouTube channel",
+			Input:    "https://www.youtube.com/@MattermostHQ",
+			Expected: nil,
+		},
+	} {
+		t.Run(testCase.Name, func(t *testing.T) {
+			assert.Equal(t, testCase.Expected, FindEndpointForURL(testCase.Input))
+		})
+	}
+}