Use XML.parse instead of XML.parse_html

Due to recent changes to libxml2 (between 2.9.14 and 2.10.4,
See https://gitlab.gnome.org/GNOME/libxml2/-/issues/508), the
HTML parser doesn't take into account the namespaces (xmlns).

Because HTML shouldn't contain namespaces anyway, there is no
reason for use to keep using it. But switching to the XML
parser means that we have to pass the namespaces to every
single 'xpath_node(s)' method for it to be able to properly
navigate the XML structure.

src/invidious/channels/channels.cr

@@ -159,12 +159,18 @@ def fetch_channel(ucid, pull_all_videos : Bool)
   LOGGER.debug("fetch_channel: #{ucid}")
   LOGGER.trace("fetch_channel: #{ucid} : pull_all_videos = #{pull_all_videos}")
 
+  namespaces = {
+    "yt"      => "http://www.youtube.com/xml/schemas/2015",
+    "media"   => "http://search.yahoo.com/mrss/",
+    "default" => "http://www.w3.org/2005/Atom",
+  }
+
   LOGGER.trace("fetch_channel: #{ucid} : Downloading RSS feed")
   rss = YT_POOL.client &.get("/feeds/videos.xml?channel_id=#{ucid}").body
   LOGGER.trace("fetch_channel: #{ucid} : Parsing RSS feed")
-  rss = XML.parse_html(rss)
+  rss = XML.parse(rss)
 
-  author = rss.xpath_node(%q(//feed/title))
+  author = rss.xpath_node("//default:feed/default:title", namespaces)
   if !author
     raise InfoException.new("Deleted or invalid channel")
   end
@@ -192,15 +198,23 @@ def fetch_channel(ucid, pull_all_videos : Bool)
   videos, continuation = IV::Channel::Tabs.get_videos(channel)
 
   LOGGER.trace("fetch_channel: #{ucid} : Extracting videos from channel RSS feed")
-  rss.xpath_nodes("//feed/entry").each do |entry|
-    video_id = entry.xpath_node("videoid").not_nil!.content
-    title = entry.xpath_node("title").not_nil!.content
-    published = Time.parse_rfc3339(entry.xpath_node("published").not_nil!.content)
-    updated = Time.parse_rfc3339(entry.xpath_node("updated").not_nil!.content)
-    author = entry.xpath_node("author/name").not_nil!.content
-    ucid = entry.xpath_node("channelid").not_nil!.content
-    views = entry.xpath_node("group/community/statistics").try &.["views"]?.try &.to_i64?
-    views ||= 0_i64
+  rss.xpath_nodes("//default:feed/default:entry", namespaces).each do |entry|
+    video_id = entry.xpath_node("yt:videoid", namespaces).not_nil!.content
+    title = entry.xpath_node("default:title", namespaces).not_nil!.content
+
+    published = Time.parse_rfc3339(
+      entry.xpath_node("default:published", namespaces).not_nil!.content
+    )
+    updated = Time.parse_rfc3339(
+      entry.xpath_node("default:updated", namespaces).not_nil!.content
+    )
+
+    author = entry.xpath_node("default:author/default:name", namespaces).not_nil!.content
+    ucid = entry.xpath_node("yt:channelid", namespaces).not_nil!.content
+
+    views = entry
+      .xpath_node("media:group/media:community/media:statistics", namespaces)
+      .try &.["views"]?.try &.to_i64? || 0_i64
 
     channel_video = videos
       .select(SearchVideo)