Fix EZP-22480: Object creation does not respect attribute constraints in ezoe

JIRA: https://jira.ez.no/browse/EZP-22480

# Description

The object creation provided by Online Editor does not check the constraints defined on each attribute. As a result, it is possible to create content objects which are not valid (for instance with too many characters in a text line attribute)

This patch makes sure the content object created by this mean are valid.

# Tests

manual tests