Remove unused mark_for_deletion functionality

[dougal]

Found some unused functionality while spelunking the codebase. Of course this might be used with tools you have not published. Below is what I wrote in the first commit:

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• The functionality provided by this was never used in other modules.
• Record deletion is always done using Repo.delete directly.
• No tests exercised this code.
• Code is almost identical to same pattern shown in Ecto.Changelog docs.
• Code appears to have been pasted from model-to-model as more were added.

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Thanks for open-sourcing, I learnt a lot, including the mark_for_deletion pattern.

[dougal]

s/methods/functions/

[jerodsanto]

Thanks for contributing! Code spelunking is fun 🔍

I haven't looked at this for awhile, but I'm pretty sure that these are necessary as the related Changelog.Episode will call cast_assoc when its changeset is processed via the admin form. That, in turn, calls changeset on the associated records, which calls mark_for_deletion. If the virtual attribute has been set via the params, the record will be deleted.

You are totally right that I haven't tested this well (there are not many tests in the admin), but you could test manually (or add tests!) by setting up an episode with some hosts/guests/channels/sponsors and then try deleting those associations on your branch. (I don't think it'll work.)

Thanks again, I love how many folks are taking the code for a spin! 💚

[dougal]

Yes, you are right, these are in fact used. In the templates the :delete virtual field is referenced for use in checkboxes for the deletion of things like guests or hosts from episodes.

If only I'd noticed this I could have submitted some tests instead. Thanks for the reply.

[jerodsanto]

No worries, it is subtle and undocumented.