Feature/bluesky link previews

[kfuras]

This pull request introduces significant improvements to the Bluesky social integration, primarily by enhancing how posts with URLs are handled and refactoring the post and comment logic for better maintainability and richer content embedding. The main highlights are the addition of Open Graph (OG) card support for posts containing URLs, a refactored posting workflow to support threads and replies, and the removal of some outdated or redundant code.

Enhancements to link embedding and post workflow:

• Added Open Graph card support: Posts without media but containing a URL now automatically generate an external embed card using OG metadata (title, description, image), providing richer previews in Bluesky posts. (fetchOpenGraphData, createExternalEmbed, extractFirstUrl functions)
• Refactored post creation logic: The post method now loops through all post details, handling media, OG card embeds, and thread/reply relationships in a unified workflow. This enables multi-post threads and improved reply handling. [1] [2] [3] [4]

Codebase and interface improvements:

• Removed obsolete methods and simplified agent initialization: The getAgent and uploadMediaForPost methods were inlined or removed for clarity, and agent initialization is now handled directly in the post method. [1] [2]
• Improved error handling and robustness: Added error handling for OG data fetching and thumbnail upload, ensuring the post process continues even if some metadata cannot be retrieved.
• Minor interface tweaks: Removed an outdated tooltip about two-factor authentication and fixed the generateAuthUrl method to return an empty URL. [1] [2]

These changes collectively make the Bluesky provider more robust, user-friendly, and capable of producing richer, more engaging posts.

[vercel]

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[sentry]

Bug: In Bluesky threads with more than two posts, the reply.root and reply.parent references are swapped, causing incorrect threading.
_{Severity: HIGH}

Suggested Fix

Swap the values assigned to the root and parent properties within the reply object. The root property should use loadUri and loadCid to reference the first post. The parent property should use replyUri and replyCid to reference the immediately preceding post.

Prompt for AI Agent

Review the code at the location below. A potential bug has been identified by an AI
agent.
Verify if this is a real issue. If it is, propose a fix; if not, explain why it's not
valid.

Location:
libraries/nestjs-libraries/src/integrations/social/bluesky.provider.ts#L461-L467

Potential issue: When creating a Bluesky thread with three or more posts, the reply
references are incorrectly assigned starting from the third post. The `reply.root`
object, which should consistently point to the first post of the thread, is instead
assigned the URI and CID of the immediately preceding post. Conversely, the
`reply.parent` object, which should point to the preceding post, is assigned the
references of the first post. This swap will cause Bluesky to either reject the posts or
display the thread with an incorrect structure.

_{Did we get this right? 👍 / 👎 to inform future reviews.}