Parse channel handle and display it on channel page and API

[Fijxu]

It also fixes some inconsistencies with the CSS and HTML that was introduced in #5617 but I didn't really noticed about because it looked fine in the Invidious frontend.

I also added a comment about the break statement in the metadata_rows row iteration because I didn't get why that break was there in the first place.

Closes #5638

---

Looks like this in the Invidious frontend (with borders enabled just to see each element sizes and limits):

The API looks like this:

  ...
  "author": "Fijxu - Topic",
  "authorHandle": "@Fijxuu",
  "authorId": "UCw-aR42z5gUcarpPGN5OKfA",
  ...

[Copilot]

Pull request overview

This PR adds channel handle parsing and display functionality to Invidious, addressing issue #5638. It extracts the channel handle (e.g., @username) from YouTube's metadata and displays it on the channel page alongside the channel name and pronouns. The change also exposes the handle in the API response.

Changes:

• Parses channel handle from YouTube metadata and stores it in the AboutChannel record
• Displays channel handle on the channel page below the channel name
• Adds channel handle to the API response for channel endpoints
• Refactors CSS classes to match the new HTML structure

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 5 comments.

File	Description
src/invidious/channels/about.cr	Adds author_handle field to AboutChannel record and parsing logic to extract it from metadata
src/invidious/routes/api/v1/channels.cr	Adds authorHandle field to the JSON API response
src/invidious/views/components/channel_info.ecr	Updates HTML template to display channel handle with restructured CSS classes
assets/css/default.css	Updates CSS selectors to match new HTML structure

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[ashleyirispuppy143]

why rename author_handle to channel_handle? the channel id and like the channel name and stuff is called author so why the handle wouldnt be?

[Fijxu]

channel_handle

Just to be consistent by how is set in src/invidious/helpers/serialized_yt_data.cr! If any other maintainer wants to change it to author_handle, I'll change it. I really have no preference, once the new key is set, people that use the API will use that and is not going to be changed as it will be a breaking change ;)

[SamantazFox]

You can combine that in a single if statement:

Suggested change

	channel_handle_part = metadata_parts.try &.as_a.find { |i| i.dig?("text", "content").try &.as_s.includes?("@") }
	if !channel_handle_part.nil?
	if channel_handle_part = metadata_parts.try &.as_a.find { |i| i.dig?("text", "content").try &.as_s.includes?("@") }

[SamantazFox]

(And similarly, you can do this to the other if statements in this .each loop)

[ashleyirispuppy143]

weh, is this never gonna get merged... :c

i have to patch my invidious every update lmao