Inconsistent conversion in `CreationDialogPropertiesCreationHandler`

[kdambekalns]

Description

The CreationDialogPropertiesCreationHandler does property value conversion from "raw" to "typed" on it's own, and in a different way compared to the NodeConverter from the Content Repository or even the NodePropertyConversionService from the UI itself.

Steps to Reproduce

1. Create a nodetype with a datetime property
2. Create a node using the creation dialog
3. Create such a node without the creation dialog
4. Compare the stored dattime values in the database

Expected behavior

The same timezone handling is applied, dates are stored in the server's default timezone.

Actual behavior

Dates are stored in the users' timezone, as sent by the browser.

Affected Versions

UI: 8.3 (and earlier)