Color Picker: Validate uniqueness of selected colors

[Programeerik]

Prerequisites

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

If there's an existing issue for this PR then this fixes #20359

Description

I've added an check on duplicates after the valid color check, so it's only checked when it's an valid color.
I've added an function normalize to the internal ColorListValidator class so the logic is much better readable.
The normalize function is for removing the # before checking for duplicate values.
When the count of duplicates is higher than 0 it's not possible to save the data.

I've also added an unittest which check if the test returns the duplicate value

[github-actions]

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[Copilot]

Pull Request Overview

This PR adds validation to prevent duplicate color values in the Color Picker property editor configuration. The validation normalizes color values (converting 3-digit hex to 6-digit format and ensuring case-insensitive comparison) before checking for duplicates.

Key changes:

• Added duplicate color validation logic with normalization for proper comparison
• Modernized the validator implementation using source-generated regex and collection expressions
• Added comprehensive unit tests to verify the duplicate validation functionality

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
src/Umbraco.Infrastructure/PropertyEditors/ColorPickerConfigurationEditor.cs	Added duplicate validation logic, normalization method, and modernized code with source-generated regex
tests/Umbraco.Tests.UnitTests/Umbraco.Core/PropertyEditors/ColorListValidatorTest.cs	Added unit test to verify duplicate color validation works correctly

[AndyButland]

Thanks for this contribution @Programeerik. I tested out and found an issue via the unit test (so that was very valuable to add), which I've fixed up and just done a little tidy up of the file since we are editing it.

Please let me know if all looks good to you and we can merge this in.

Moving forward I'd like to see better surfacing of this validation in the backoffice itself (which works well for content, but less so for data type configuration), but having this improved check on the server-side is worth having anyway.

[Programeerik]

@AndyButland Great point about the continue addition. When you talk about the validation in the backoffice, do you mean so that the user get realtime feedback?

The serverside code check can be merged. Thanks for the additions and help.

[AndyButland]

When you talk about the validation in the backoffice, do you mean so that the user get realtime feedback?

Could be real-time, but more that we better surface the server-side validation when managing data type configurations.

[bjarnef]

@AndyButland should we consider some of these changes in ValueListUniqueValueValidator (of course in a new PR):

Umbraco-CMS/src/Umbraco.Infrastructure/PropertyEditors/ValueListUniqueValueValidator.cs

Lines 47 to 52 in 767894b

	var duplicateValues = items
	.Select(item => item)
	.GroupBy(v => v)
	.Where(group => group.Count() > 1)
	.Select(group => group.First())
	.ToArray();

It seems .Select(item => item) is redundant - and I think HashSet may perform better.

[AndyButland]

Looks like it, certainly the Select is redundant but can't see it does any harm. As you say, I don't think it would be part of this PR (which I've merged now anyway!),