For some reason dam 2.4 doesn't depend on 5.7 yet.

• release/2.3 is the 5.6-compatible branch
• there's a compilation issues because of the decoupling from Vaadin's deprecated Converter API
  • see info.magnolia.ui.form.field.converter.FieldValueConverter (Magnolia replacement)
  • see MGNLUI-4363

Then the update turned out to be more complicated, primarily on AssetLinkFieldFactoryTest:

• #linkField_SetFieldPropagation starts to fail because the value propagation to the inner text-field *is* effectively broken in this scenario (textField never has a datasource of his own anymore, since MGNLUI-4368)
  • analog test in UI's LinkFieldFactoryTest passes by cheating, because the last assertion was made completely bogus (yay, testing Vaadin's #setValue ftw)

Turns out AssetLinkFieldFactory is an obsolete/duplicate of an old version of UI's LinkFieldFactory. We should:

• Deprecate and phase out usage of AssetLinkField, since it does not have any value on top of the stock LinkField
• Make AssetLinkFieldFactory extend LinkFieldFactory instead of copy-pasta
• Keep merely the #createChooseDialogCallback method, that's the one feeding the choose-dialog selected value back as a DAM ItemKey to the LinkField.

When doing the above, AssetLinkFieldFactoryTest#simpleLinkFieldUuidTest starts to fail too:

• because the stock LinkFieldFactory passes the identifierToPathConverter via LinkField#setTextFieldConverter
• the AssetLinkFieldFactory does not handle identifierToPathConverter at all —nor contentPreview, fwiw.
  • confirmed by commenting out this behavior from super implementation, test passes again...
• surprising, given documentation examples include the identifierToPathConverter in configuration.
  • see [https://documentation.magnolia-cms.com/display/DOCS57/External+DAM+app+module|External DAM app module]
  • see [https://git.magnolia-cms.com/projects/DOCUMENTATION/repos/cumulus-templates-examples/browse/dialogs/components/cumulusSimpleImage.yaml#9|cumulusSimpleImage.yaml]

We should check dam-external-app (via cumulus or S3 module) on 5.7, and figure out what it used to do when identifierToPathConverter is configured.