Catalogue item hierarchy support (sub-dataset)

[meericsc]

Currently, REMS does not support referencing one catalogue item to another. Bigpicture project would need to support the concept of datasets and additional "complementary" datasets.

Add ability to mark a catalogue item as "part of" another catalogue item

• Add "part of" to catalogue item in UI (json blob, postgres catalogue item data)

• API support (optional field)

• In catalogue item editor add field where you can add and edit this info (e.g., Dataset A is part of Dataset B)

• Tests + documentation

• Related is the logic that allows only applying access to subdatasets if also the main dataset is added to application: Validate application before sending #3411