Add url calculation to attachment resource

[sodapopcan]

Contributor checklist

Leave anything that you believe does not apply unchecked.

• I accept the AI Policy, or AI was not used in the creation of this PR.
• Bug fixes include regression tests
• Chores
• Documentation changes
• Features include unit/acceptance tests
• Refactoring
• Update dependencies

First off, sorry @StephanH90 if you were planning on doing this, I just wanted this ASAP so I put this together. If you have WIP you were hoping to PR, I'm happy to close this in favour of anything you've done (not a loss for me as I learned a thing or two!)

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Adds url directly to the attachment resource as per #5.

Design Trade-off

This implementation threads the parent resource through the calculation in order to get the base_url. Alternatively, we could store the base_url in AshStorage.Service.Disk.service_opts_fields however this would be a breaking change. Note that it would only be breaking for users who would want to use this new functionality and in order to do so, would need to back-fill.

Basically this:

defmodule MyApp.Repo.Migrations.BackfillBlobBaseUrl do
  use Ecto.Migration

  def up do
    execute """
    UPDATE storage_blobs
    SET service_opts = jsonb_set(COALESCE(service_opts, '{}'), '{base_url}', '"/storage"')
    WHERE service_name = 'Elixir.AshStorage.Service.Disk'
    AND (service_opts IS NULL OR NOT service_opts ? 'base_url')
    """
  end

  def down do
    execute """
    UPDATE storage_blobs
    SET service_opts = service_opts - 'base_url'
    WHERE service_name = 'Elixir.AshStorage.Service.Disk'
    """
  end
end

I want to note that I use AI heavily to produce these changes. I spent around 1.5 hours on this PR going back and forth with Calude Code, gaining a decent grasp of what is going on but I cannot say that I yet have a deep understanding of the inner workings of ash_storage (having built things like this before I have a very good high level understanding I'm just talking more Ash stuff, like Spark).

I have also tried this out in my current project and all seems good there.

[sodapopcan]

Also, small nitpick I noticed: all calculations define an init/1 that doesn't do anything different than the default. I just did the same though if they are unnecessary this seems like a decent PR to remove them in.

[zachdaniel]

Down to remove the unnecessary callbacks. Was using them at some point and removed the check w/o removing the callback.

[zachdaniel]

Down to remove the unnecessary callbacks. Was using them at some point and removed the check w/o removing the callback.

[sodapopcan]

Down to remove the unnecessary callbacks. Was using them at some point and removed the check w/o removing the callback.

Done!

[sodapopcan]

I'm working through the CI issues.

[sodapopcan]

I'm having a very hard time understanding what is wrong with CI. if Code.ensure_loaded?(Phoenix.PubSub) is directly above the line that fails on a call to Phoenix.PubSub.broadcast. It seems to be happening in main as well, though, at least locally. I'm a bit at a loss atm the moment but I can come back to it if this isn't familiar to you.

[zachdaniel]

🚀 Thank you for your contribution! 🚀

(we just need to use apply there)

[sodapopcan]

Oh, I could have made that change before you merged! AI actually suggested exactly this change but I wasn't sure about it 😅

[zachdaniel]

It's all good, was easy enough to update! I was excited to get this in 😆