Deprecation: #66588 - POST Data in selectviewhelper should have higher priority than "value" value

See forge#66588

Description

Submitted form data has precedence over value arguments.

This adjusts the behavior of all Form ViewHelpers so that any submitted value is redisplayed even if a "value" argument has been specified.

The issue with this, however, was that upon re-display of the form due to property-mapping or validation errors the value argument had precedence over the previously submitted value.

Impact

This is a breaking change if you expect the previous behavior of form ViewHelpers always being pre-populated with the specified value attribute / bound object property even when re-displaying the form upon validation errors.

Besides this the change marks AbstractFormFieldViewHelper::getValue() as deprecated. If you call that method in your custom ViewHelpers you should use AbstractFormFieldViewHelper::getValueAttribute() instead and call AbstractFormFieldViewHelper::addAdditionalIdentityPropertiesIfNeeded() explicitly if the ViewHelper might be bound to (sub)entities.

The default usage of getValueAttribute() did not respect the submitted form data, because not every viewhelper needs this feature. But you can enable the usage of the form data by setting AbstractFormFieldViewHelper::respectSubmittedDataValue to TRUE.