Define mandatory fields for pin fields

As a project manager, I would like to be able to specify that certain fields in a pin must be completed - either when the pin is created or at the latest before it is closed.

This is to ensure that important information is not missing and that structured work processes are adhered to. The behavior could be based on the existing mandatory field "Pin title". This function is particularly relevant for weight recording, safety-relevant information or unique dataset links, for example.