Refactor GetChildren method on Content Controller and introduce GetChildrenForSort

[AdamPrendergast]

I've just pushed some updates that hopefully tackle the issue discussed here https://github.com/umbraco/Umbraco-CMS/issues/15608

This is a draft PR, so consider this a potential option for a fix. There maybe other options we can explore, so any feedback would be welcome :)

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Introduced the GetChildrenFilter class for parameter encapsulation to enable a DRY approach.

This change facilitates the introduction of a new GetChildrenForSort method, allowing precise control over the ActionLetter in the FilterAllowedOutgoingContent.

Added the GetChildrenFilter to 'Umbraco.Cms.Core.Models.ContentEditing' as there seemed to be president with GetAvailableCompositionsFilter

Prerequisites

• [ x] I have added steps to test this contribution in the description below

Description

For reference: please see videos of the original bug here: https://github.com/umbraco/Umbraco-CMS/issues/15608

On a fresh install setup a new editor user and create a simple multi root node structure:

For the created user setup a new group:

• Content start node to be on of the root nodes
• Restrict the permission so only Sort is enabled in the Structure settings.

Set 'Granular permissions' for the start node as:

Assign this group to the created editor user.

Sign in as the editor user.

The Content should be restricted as expected.

The user should now be able to sort the nodes

[github-actions[bot]]

Hi there @AdamPrendergast, thank you for this contribution! 👍

While we wait for one of the Core Collaborators team to have a look at your work, we wanted to let you know about that we have a checklist for some of the things we will consider during review:

• It's clear what problem this is solving, there's a connected issue or a description of what the changes do and how to test them
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[mikecp]

Hi @AdamPrendergast,

Thanks for your PR and for the detailed explanations on how to test this 👍 Someone from the core collaborators team will have a look at it soon.

[AdamPrendergast]

Great, thanks @mikecp

Happy to implement any feedback or take a different approach if desired.

[AdamPrendergast]

Thanks for the feedback @nul800sebastiaan

I had approached this thinking that that Content Controller was only used by the Backoffice code itself. Thanks for pointing out that it is indeed a public API - which does change matters.

I might have to go back to the drawing board with this one to work out if there is an 'elegant-ish' way of handling the permission value that is set in the FilterAllowedOutgoingContent attribute.

If it is not possible in a way the is maintainable/sensible, I wonder if we just need to stipulate that in order to 'sort' nodes, a user requires 'browse' permission (which makes sense to me).

This could then be a documentation update, or even a message in the permission management section - just a thought.