FEATURE: Add notEmpty validation for asset metadata fields and improve UI feedback

[Alvadda]

This PR adds validation for the title and alt fields per image in both the single editor and the collection editor.

To enable validation, add a validation configuration with the notEmpty rule and specify the fields to validate (e.g. alt, title). This ensures that the UI correctly reflects the validation state for users in both editor variants.

To prevent users from applying an invalid configuration, a corresponding server-side validator must also be provided. The validator
Sitegeist.Kaleidoscope.ValueObjects/Validators/NotEmpty mirrors the structure of the validation configuration defined in editorOptions, ensuring consistent validation behavior between the UI and backend.

    image:
      ui:
        inspector:
          editorOptions:
            crop:
              aspectRatio:
                forceCrop: true
                locked:
                  width: 4
                  height: 3
            validation:
              notEmpty:
                alt: true
                title: true
      validation:
        'Sitegeist.Kaleidoscope.ValueObjects/Validators/NotEmpty':
          alt: true
          title: true

[mficzel]

I ran straight into this when creating a new content with enabled validation:

Name: TypeError

Message: Cannot read properties of null (reading 'alt')

Stacktrace: TypeError: Cannot read properties of null (reading 'alt')
    at isValueValid (https://site-de.ddev.site/_Resources/Static/Packages/Sitegeist.Kaleidoscope.ValueObjects/JavaScript/Plugin.js?bust=d2948a2f:6010:62)
    at NotEmpty (https://site-de.ddev.site/_Resources/Static/Packages/Sitegeist.Kaleidoscope.ValueObjects/JavaScript/Plugin.js?bust=d2948a2f:6029:10)
    at n (https://site-de.ddev.site/_Resources/Static/Packages/Neos.Neos.Ui.Compiled/Build/Host.js?bust=baef9f8c:15:102013)
    at https://site-de.ddev.site/_Resources/Static/Packages/Neos.Neos.Ui.Compiled/Build/Host.js?bust=baef9f8c:15:102151
    at Array.map (<anonymous>)
    at Gee (https://site-de.ddev.site/_Resources/Static/Packages/Neos.Neos.Ui.Compiled/Build/Host.js?bust=baef9f8c:15:102125)
    at https://site-de.ddev.site/_Resources/Static/Packages/Neos.Neos.Ui.Compiled/Build/Host.js?bust=baef9f8c:15:102312
    at Array.forEach (<anonymous>)
    at REt (https://site-de.ddev.site/_Resources/Static/Packages/Neos.Neos.Ui.Compiled/Build/Host.js?bust=baef9f8c:15:102265)
    at https://site-de.ddev.site/_Resources/Static/Packages/Neos.Neos.Ui.Compiled/Build/Host.js?bust=baef9f8c:15:103396

to reproduce: create content that has an image with enabled validation, select content that has no image selected yet

[mficzel]

Works fine now in general. I suggest to

1. Remove the mentioning of "Sitegeist.Kaleidoscope.ValueObjects/Validators/NotEmpty" that is not implemented and also does not work properly anyways. The feature here is merely editor support and does not gain much by additional serverside validation
2. Translate the Error message at least into de / en / fr (add Xliff files in Resources/Private/Translations + Setting Neos.Neos.userInterface.translation.autoInclude.Sitegeist.Kaleidoscope.ValueObjects)
3. When the be validation is not configured the error message is not shown but the value can be applied ... this may be intentional and also solve the translation issue before as it merly hints and not enforces hard

[Alvadda]

Works fine now in general. I suggest to

1. Remove the mentioning of "Sitegeist.Kaleidoscope.ValueObjects/Validators/NotEmpty" that is not implemented and also does not work properly anyways. The feature here is merely editor support and does not gain much by additional serverside validation
2. Translate the Error message at least into de / en / fr (add Xliff files in Resources/Private/Translations + Setting Neos.Neos.userInterface.translation.autoInclude.Sitegeist.Kaleidoscope.ValueObjects)
3. When the be validation is not configured the error message is not shown but the value can be applied ... this may be intentional and also solve the translation issue before as it merly hints and not enforces hard

Added Translations to the Package

Translation Package name: Sitegeist.Kaleidoscope.ValueObjects
Translation key for Validation: validation

New Translations:

validation.missingAlt
validation.missingTitle
validation.missingTitleAndAlt
validation.collectionItemMissingAlt
validation.collectionItemMissingTitle
validation.collectionItemMissingTitleAndAlt