Add Dataset Object Type

[OpenDataAlex]

Extracts should be associated to a dataset type. Instead of it's own object, maybe associate to Source?

[OpenDataAlex]

Data sets could be things like 'Customer' or 'Department Stats'.

[OpenDataAlex]

Implementing by adding a new lookup type - dataset_topic_lkup. This will associate with Processes, Extracts, Sources, and Source Objects.

[OpenDataAlex]

Also need to add option to add new dataset types to CLI.