feat(channels): Add support for Bluesky

[ERosendo]

This PR fixes #398.

Here's a summary of the changes introduced by this PR:

1. Registers Bluesky as a new channel and adds a new client class to handle requests to the Bluesky API. This custom client uses the Bluesky API to handle post creation and media uploads. Although the Bluesky Python API clients listed on the website are still under development, Our class focuses on the essential functionalities required for the bot's operations.

2. Integrate the new Bluesky API class to the Channel class properties

3. Refines validation logic in the add-a-case form.

   While testing the Bluesky API integration, I noticed that the platform handles links differently from Mastodon and X. Unlike Mastodon/X, Bluesky uses the full length of links. This discrepancy could lead to posts exceeding the character limit of the template, as the template class doesn't truncate content in such instances. The enhancement ensures that the combined length of the post's name, summary, and link adheres to the maximum allowable length. Additionally, an informative error message is now displayed to users when the content exceeds the limit. This message instructs users to modify the content of the form, possibly by using a different combination of name, summary, and link, and resubmit it for successful posting. Here's a screenshot of the error message

4. Add templates for new cases and regular posts.

[mlissner]

This looks great. A few comments, thank you!

One question. On Blue Sky, it seems that clients are responsible for including link previews when posting (they call these "cards"), instead of the server doing that work. is that correct? If so, do we do that? Do our posts come with previews or no?

[ERosendo]

@mlissner this PR is ready for another review. All the typos are fixed and I updated the templates to embed links within the text.

it seems that clients are responsible for including link previews when posting (they call these "cards"), instead of the server doing that work. is that correct?

You're right, the client has to extract the metadata from the link to build previews

Do our posts come with previews or no?

I added a helper method to automatically display link previews in posts when the post doesn't show thumbnails. Here are some screenshots:

[mlissner]

A few tweaks, but otherwise looks good. Merge when ready!

[sentry-io]

Suspect Issues

This pull request was deployed and Sentry observed the following issues:

• ‼️ Exception: image file size too large. 1000000 bytes maximum, got: 1173173 bc.subscription.tasks.make_post_for_webhook_event View Issue
• ‼️ TypeError: Session.init() got an unexpected keyword argument 'error' bc.subscription.tasks.make_post_for_webhook_event View Issue

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